32 



A B C OF THE STEEL SQUARE 



12 inches. E is at a point 5 inches from B, 

 ;ind C 12 inches from B. B-A represents the 

 run of the common rafter. E-A represents the 



C B 



Fig. 52. 



run of the octagon hap or valley, and C-A thf 

 same for the common hip or valley, their lengths, 

 being 12, 13, and 17 respectively. Now since 

 12, 13, and 17 are fixed numbers, we take them 

 on the tongue of the square, as shown m Fig. 52. 



