52 A B C OF THE STEEL SQUARE 



the twelve-inch mark on both sides of the 

 square carefully on the backing line, and 

 marking off the rafter on the outside edges of 

 the square. Repeat this until you have fifteen 

 spaces marked off, then set back from your last 

 mark half the thickness of the ridge-board, and 

 with the square as before mark off the rafter. 

 This will be the exact length and also the 

 plumb-cut to fit the ridge-board. Or if we take 

 the diagonal of 12 by 12, which is 17, and mark 

 off 15 spaces of 17 in., making the necessary 

 allowance for the half thickness of the ridge- 

 board, it will amount to the same thing, every 

 17 in. on the rafter being nearly equal to one 

 foot on the level. 



Should the building measure 30 ft., 9 in. in 

 width the half of which is 15 ft., 4% i n - w ? 

 take the fifteen spaces of 12 by 12 and then the 

 4 1 /o in. on both sides of the square on the back- 

 ing line as before. This will give us the extra 

 length required. The same rule will apply to 

 any portion of a foot there may be. 



A fence, sometimes called a stair gauge, is 

 manufactured of metal by the Cheney & Tower 

 Company, Athol, Mass., which I show at Fig. 

 28, and is considered about the best thing of 

 the kind. It consists of a piece of polished 

 angle metal, each side being % inch wide. One 



