Builders must know when string lines are square, foundations and floors are level, and walls are plumb (vertical) and square to each other. Since the beginning of history, four simple instruments have been used to test for these - the plumb line, the A frame, the plumb board, and the 3-4-5 square. They were known in ancient Egypt, Babylon, and China, to name just three, and ever since, builders have been making them from scrap timber, and discarding them at the end of each job. The plumb line has been covered in Chapter 1. The Try-all is a 3-4-5 square which will do all these tasks in one instrument.


The A Frame & Plumb Board are aids for the plumb line; the A frame lets horizontal surfaces be checked for level, while the plumb board gives the plumb bob enough clearance for checking vertical surfaces. Like this:-

One of the advantages of the A frame is that only the ends of the legs touch the surface under test, so almost anything long and thin, but not necessarily straight, can be lashed or nailed together to make one - bamboo poles, old boards, even iron star pickets. Crossing the legs at the top makes a V shape, to hold the line always in the same place. To align the A frame:-

1. Stand it on a bare surface, not necessarily level, and faintly mark where the line hangs.
2. Turn the frame round the other way (180º), stand it on the same points., and again mark where the line comes.
3. Put a strong mark on the frame exactly half way between the first two marks. This is the level point. Like this:-

The Plumb Board touches the surface under test along its whole length, so a board with at least one straight edge is needed. If this is not available, cut away most of the edge, leaving small sections at each end, like this:-


Aligning a plumb board can be done two ways; if the board has both long edges straight and parallel with each other, the board can be turned around like the A frame.



1 Place one edge of the board against an upright but not necessarily vertical surface, and lightly mark the board where the line comes to rest.
2. Turn the board back to front, place the other edge against the surface, and again lightly mark where the line comes.
3. Put a heavy mark exactly half way between the first two. This is the plumb point. Like this:-


The second method requires a pole, column, or pipe held vertically (e.g. a length of water pipe with one end in the ground).

1. Place one edge of the board against one side of the pipe and mark where the line comes.
2. Turn the board back to front, and place the same edge against the opposite side of the pipe. Again mark the board.
3. As in (3) above.



The 3-4-5 Square Frame was well known before Pythagorus wrote his famous theorem - any triangle with sides in these proportions has one angle a right angle (Square). Builders need one larger than an ordinary square, and usually make it from scrap timber. The sketch and chart show several sizes, in both Metric and Imperial measurements. The proportions 3:4:5 are easy to remember, but a 45 degree angle between the brace and the arms is more useful, so measurements for this are included. Paint it a light colour for easy visibility.




The Try-all is a combined A frame, Plumb Board, and 3-4--5 square, with a length of dowel or wire as a pendulum on the vertical arm (arm 1). It will check level, plumb, and square with enough accuracy for small construction work. When folded, it takes about the same room in the tool box as a. bubble level. To make it, you need a length of straight grained dressed timber, preferably hardwood, (or three short lengths), a short length of dowel, narrow bamboo stick, fencing wire, or a wire coat hanger, three eyebolts and tee nuts (if available), a screw eye, and five machine screws and nuts . THAT’S ALL !

For checking level and/or plumb, the Try-all is held with the lower arm (arm 2) horizontal and arm 1 vertical. When the bottom of the pendulum is hanging over a ‘plumb’ mark, arm 1 is plumb and arm 2 is level - the pendulum works like a plumb line, but can’t swing about because of the stop screws or tube (see later). And you don’t have to wind it up when finished. Reading its position is a little harder than reading a bubble, but it is as sensitive and accurate as the same size builders’ level. Like this:-

Construction. Mark and drill all holes shown in fig.2-1, except the ones labelled with **. Don’t cut the pendulum to length yet.
Lay the arms and brace in their correct positions, flat on a bench with the brace side up. Match the joining points and if possible clamp everything. Now drill the holes marked ** , through both arms and brace at the same time, and as close to the centre lines of arms and brace as possible.

Mark the outlines of the brace where it crosses the arms, and use these marks as a guide for cutting away the arms a little to allow the brace to sit on a slight angle, as in Fig.2-2. Use the hole at the bottom of arm 1 as a guide for drilling the end of arm 2 and the block. Assemble the frame and block, and file the bottom face of the block, the bottom end of arm 1, and the bottom edge of arm 2, flush and square across to help the frame stand upright. Also cut off both ends of the brace, flush with the sides of the arms.

To make the pendulum from dowel, screw a small screw eye in one end of it, as accurately as possible in the centre. To use a bamboo stick, it may be necessary to plug one end with a small wood plug to take the screweye. Check for any rough spots on the inside of the rings where the eyes will link, and smooth these with a small round file or emery paper. Link the eyes together; it may be necessary to bend one of the eyes open to do this. Screw the top eyebolt in, with its eye in line with the arm, and hang the dowel down in position. Stand the frame upright and make sure the pendulum swings freely; if the bottom hits the block, cut it a little shorter. Then put in the stop screws.

To make the pendulum from wire, first straighten it out, then turn a loop on one end. The pendulum length will depend on the size of eye bolt or screw eye; make it a little too long, and cut it back later. If the frame is to be painted, do this next, and let the paint dry, to keep paint off the screw eyes or the wire loop.

A better idea is to put a wire pendulum inside a length of aluminium or brass tubing or copper pipe, about 20 to 30 mm. diameter, to shield it from the wind. Do NOT use plastic tube or conduit, which can generate static electricity and upset the pendulum. Steel or iron pipe can only be used with a non-magnetic pendulum made of brass or copper wire, wood dowel, or bamboo stick.

Mount the tube on arm 1 with saddles, or tie it on with wire. Link the loop and eye together, feed the wire down the inside of the tube, and screw the top eyebolt in, with its eye in line with the arm. Stand the frame upright; the pendulum should now be hanging down inside the tube. Make sure it swings freely; if the bottom hits the block, cut it a little shorter. The brace will now have to be screwed to the back of arm 2, and will also be on the back when the try-all is folded. Like this:-






Figs. 2-1, 2-2, and the following sketches all show a dowel pendulum, but the construction and alignment for a wire pendulum, with or without the shield, is the same.










To Align the Try-all:-
1. Place a stop & wedge on a bench, or clamp a straight edge in a vice, and stand the Try-all on top. Then hold a plumb line down the edge of arm 1, like this:-

2. Move the wedge, or adjust the angle of the straight edge, until arm 1 and the plumb line are parallel.
3. Reverse the Try -all without disturbing the wedge, stop, or straight edge, like this:-
If arm 1 and the plumb line are still parallel, the frame is square,arm 2 is level and arm 1 is plumb. Go to step 5.
4. If arm 1 and plumb line don’t agree now, the frame isn’t square; make sure the joining point measurements are right and the points match each other. If there is an error, remove one of the brace screws, pull the frame square, and drill a new screw hole off centre. (Don’t try to use the old hole by drilling or filing it out; this is likely to cause trouble later when the frame is folded and re-opened ). Then repeat steps 1 to 3.



5. When you are sure the frame is square and arm 2 is level, adjust the slope of the eyebolt ring at the top of the pendulum to bring the bottom of the pendulum central between the shafts of the stop screws. Like this:-


Using the Try-all. Stand its lower arm on a horizontal surface, and when the bottom of the pendulum is central between the stop screws, that surface is level Similarly, hold the upright arm against a vertical surface; when the pendulum is centred, the surface is plumb. Or use both arms as a try square, to check whether two surfaces are square to each other, like this:-

The Try-all can be used as a guide to roughly square up string lines, by laying it flat under where the lines cross,with the edge of one arm parallel to one line, then moving the second line to be parallel with the second arm. This should be done looking straight down on it, but by painting the Try-all white for good visibility, a rough first alignment can be made from some distance away, such as the far end of the second line. String lines can be pulled out of line easily by clumps of grass or mounds of dirt, and if they are used to guide moving machinery they are often soon broken.
Left:- A Try-all being used to align string lines. Right:- A Try-all folded up.

The Try-all can be folded up by undoing the brace, folding arm 2 up behind arm 1, then sliding the brace in between the pendulum and arm 1. The whole thing can then be tied with string. If you are using tee nuts, there is a better way; slide the brace into position as above, with the tee nuts uppermost, then mark the positions of the existing holes in the brace, on the face of arm 1. Then drill two 5 mm.(3/16 in. ) holes through both arms, at the marked positions; the eyebolts can then be pushed through these holes from behind and screwed into the tee nuts to hold it all together.



 Length Measurement. There are three things used in building for this - the 3 Foot (1 yard) or 1 Metre folding carpenters’ rule, the steel tape measure in various lengths, and the long linen tape measure. Most carpenters’ squares and some spirit levels also have scales. But if you don’t have these things, there are some substitutes. A straight yard or metre stick can substitute for a folding rule, and a longer measuring rod can replace a steel tape, although they are a nuisance to carry from job to job. For longer measurements, there are both good and bad substitutes.
String or nylon fishing line is good for setting out straight lines, but stretches too much for measuring. Rope or heavy cord is better if laid on the ground and pulled tight (not strained) to stop sagging. Single or double insulated electrical cable is O.K. Dog or jack chain is satisfactory, although it does stretch a little. All these need marking in some way, which is a long job. Surveyors’ chain is made for the purpose, but is now obsolete and very hard to find.

Measuring rods don’t stretch, may not need marking (depends on use), and one person can carry either three 5 M. or five 2 M. wood or bamboo rods. An 8 M. steel tape and three 5 M. rods have a total length of 23 metres - measure in multiples of 5 until near the end, then use the tape. Make the rods a little long (For example 5.1 M.), then drill holes near each end exactly the measuring length (e.g. 5 M.) apart. Like this:-


A large nail, decking spike, or iron tent peg can be pushed through holes in two rods laid on end, then into the ground to keep them still. (Use three rods so it is obvious if one is out of place). Make the hole size just enough to take the spikes or nails you have, without being loose in the hole.

Other substitutes are lengths of pipe or conduit supplied in exact lengths. Electrical P.V.C. conduit, 4 metres long, or P.V.C. water pipe, either 5M. or 6 M. long, from the plain end to the base of the socket, are O.K.. Don’t push the end of one length into the socket of the next - the measurement will be right, but they’re hard to pull apart. Metal pipe is sometimes supplied in 21 ft. lengths. So be careful to check which length you have.

Linked measuring rods are good; five 2 metre linked rods give a total length of 10 M., and fold up neatly. Each rod has screw eyes in each end, linked at one end to a split curtain ring; the measurement is taken from the inside of the screw eye at one end, to the inside of the curtain ring at the other. Like this:-


 The rods are cut a little shorter than 2M., and the length is made up by the screw eyes and curtain ring. A screw eye in the end of the next rod is then linked to the curtain ring, and this is continued until all rods are linked together. The assembly starts with a curtain ring and ends with a blunt end; the first ring is used like the loop at the start of a linen tape - to fit over a peg or nail. The length of each rod can be adjusted by screwing the screw eyes in or out, or by altering the shape of the curtain ring to make it longer.



Left:- Five 2 M. rods, laid out in a straight line for measuring, and folded for carrying.


Laying out Offset Lines - that is, lines at an angle to a datum or reference line - can be done with measuring rods. There are too many possible combinations to show all of them, but here are a few possibilities.
1. Laying out a right angle (two lines square to each other) :-


For 2 rods, place them in position 1, put a spike through each end, then move them to position 2 without moving the spikes. Put a 4 th. spike at the join of the rods, then remove the rods and run a string line between the upper and lower spikes. With 4 rods, spike all joins, lift the rods, and run a string line between the spikes.

2. Laying out a line at 45º to a datum line. First lay out a right angle as in (1) above, then use 4 or 6 rods like this:-

3. Laying out 90º, 60º, and 30º angles:-









A Frame Slope Measurement. Height differences between the legs of an A frame can be measured with a scale made from an ordinary 300 mm. (1 foot) ruler mounted on the crossbar. One person can quickly measure a slope. The A frame can be any size, but the distance from the top of the plumb line to the top edge of the scale, must be equal to, or exactly 1/2, the distance between the leg tips. Table 3-1 gives suggested sizes. There is a slight error in the measurement, but it is very small; ground irregularities cause larger errors. Gradients up to 1 in 3 can be measured; above this the error gets larger, but most slopes are much less than this.

The frame can be made from almost any straight grained timber; the picture shows two range poles doing double duty as the legs. If screws are used to hold it together, it can be folded up.



Make the top screw an eye bolt, and tie the plumb line to the eye, which can be turned to centre the line accurately on the centre of the scale, with a quick end for end check each time the frame is unfolded.
The ruler scale must be exactly at right angles to the plumb line when the line is on the centre mark. If you use a short plumb line, the cross arm will be close to the top, and a second cross arm should be put across the bottom to keep the legs firmly in place.

Construction. Cut the legs first, about 20 mm. longer than size A in the table, to allow for the top bolt holes. Mark and drill the bolt and screw holes. Cut the crossbar; this should be longer than dimension E to allow for the screw holes. Drill only one of the screw holes, and screw the bar in place at one end. Then clamp the other end of the bar to the second leg, with the legs open top exactly 1 Metre or 1 Yard, and drill the second screw hole. Turn the eyebolt eye vertical, and measure dimension B from the bottom edge of the eye, and put a horizontal mark on the crossbar. Tie a plumb line to the eye of the bolt, and do an end for end check (see the A Frame) to find the centre point, and mark it. There should now be two marks on the cross arm, like this:- +. Drill three small holes, one at each end and one in the middle, along the ruler, and mount it with the 150 mm. point on the centre of the cross, and the scale exactly at right angles (square) to the centred plumb line.

Now do another end for end check, and if the plumb line isn’t on the 150 mm. mark when the frame is level, turn the eyebolt eye as shown for the Try-all pendulum (see above), to bring the plumb line on to the mark. Having the 150 mm. point as the centre of the scale, and calling it zero, takes getting used to; each time we take a reading, we must mentally either subtract 150 from the reading if the plumb line swings to the right, or subtract the reading from 150 if the plumb line swings to the left. To avoid this, cut the ruler just above the 150 mm. mark, and mount it with 0 mm. at the centre and the scale only on the right hand side; to read in the opposite direction, just turn the frame round the other way.
Check the instrument by putting a wood block of known height under one leg, and noting the scale reading. If you have chosen the 1/2 ratio for A and B, multiply the scale reading by two.



String Lines can hardly be called instruments, but they are probably used more than any other measuring device on building sites, to set out straight lines, to show the location of excavations for drainage, pipelines, or foundations. They are usually tied to low stiles, rather than single pegs, so their position can be adjusted later, like this:-

   



The Line Level.A string line can be used with a line bubble level. A line level is cheap, and small enough to be carried in your pocket, but must be used with care to give an accurate result. The line must be tight to avoid sag, with the level exactly in the middle. Use string with a smooth surface - a line level is light, and any hairs can tilt it. Nylon fishing line is good; it is smooth, and can be pulled very tight, which minimises sag. For best results turn the line level end for end and average the readings. Like this:-

A method for measuring slopes uses two staffs, a pre measured string line, and a line level. Both staffs are marked at the same point, around eye height. One end of the string is tied at this point to the first staff; the other end is tied in a loop to slide loosely on the second staff. The string is pulled tight and slid up or down the second staff until the line is level. Like this:-

Then the difference in height, X , equals H1-H2, and the gradient is (H1-H2) / L..


A Measuring Tape Levelling Gadget . When laying out building foundations or boundary lines, distances are measured horizontally, not along the slope of the land. An easy way is to put a line level on a measuring tape and measure to a vertical stake or plumb line. The line level can be made to fit on the tape with a wire clip, as shown in the photo. Like this :-


Make the tape hooks exactly the same length, so the tape will be horizontal when the bubble is in the middle. Keep the tape tight to avoid sag.

A U - Tube Water Level , is simply a length of flexible tube or hose, filled with water. This is the only device which will work round corners, making it useful for checking floor levels in existing buildings. If the tubing is clear so the water level can be seen, the only other thing needed is some means of sealing each end, like corks, to stop leaks when being carried. Like this:-
Air bubbles trapped in the hose will affect its accuracy; use a vigourous flow of water when filling the hose, to get rid of bubbles. Clear plastic tubing is better; it lets you see any bubbles.



Another way to make the level is to attach two plastic drink bottles to the ends of a short length of garden hose. Cut the bottoms off the bottles, or drill a small hole in each one to allow air in. The holes are better; they will stop the water surging in the hose.
Before using the level, place the bottles as high as possible, then shake the hose vigourously, and note whether any air bubbles up in either bottle. Keep the tube or hose out of the sun; heating may cause water expansion and affect the accuracy. Keep checking the reference point (point A in above diagram) to stop these errors.

This brings us to the end of the simple contact instruments. The following chapters show sighting instruments, used for a wider range of work.