A Level,
will make himself one, probably using three pieces of board, a string, and a weight, as shown in Fig. 64. The two side-pieces of wood being exact duplicates in all dimensions, the angles at the bottom are necessarily equal, and a line from the apex (A) to the centre of the bottom-piece must be a plumb line. After sawing out his side-boards and joining them at their top edges, he nails a straight piece to the bottom-ends, using the utmost care to have the lower edge of the bottom-board exactly the same distance from A on each arm; that is, A B must be exactly the length of A C, and B D must equal D C. He next cuts a small notch at A, so that he can fit a string at the crack between the two arms, A B and A C. A notch is also cut at D, to allow the weight play-room. When the lower edge of the bottom-board is placed upon a level, and the string ceases to vibrate, it will be found that, the bullet hanging free, the string exactly covers a line which has been previously ruled across the bottom-board. The line was ruled by placing a straight-edge, or rule, at A and D. The slightest incline of the base-board will throw the string to one side or the other, and show the base to be out of level.
This implement is a simple thing to construct, is as serviceable as a spirit-level, and as reliable.
For buildings, a large-sized level, with side-pieces three feet long, is useful. Smaller ones are handy in the shop.