ABC OF THE STEEL SQUARE 91 



inches on the blade, because the common rafter 

 having a rise of 10 inches to one foot, for one 

 inch it would have 1O-12 of an inch, while the 

 hip would only have 10-17 of an inch to one 

 inch and for 12 inches it would be 12 times 

 10-17 equals 120-17, or 7 1-17 inches. There- 

 fore the figures given in the second illustration 

 would give the same cuts as those in the first, 

 but as the latter necessitates a calculation that 

 ends in fractions fractions not given on the 

 square and for that reason 17 is generally used 

 for a foot run for the hips and valleys. 



AN UNEQUAL PITCH. 



In the matter of roofing over unequal pitches 

 when there is no ridge and when all hips meet, 

 the building being longer than it is wide, the 

 backing of hips and their lengths and bevels 

 would be a very easy matter if a drawing of the 

 whole thing was made, but, to obtain these by 

 the use of the square alone, is somewhat more 

 difficult. Let us assume the building to be 18 

 feet wide and 28 feet long, and having a rise of 

 9 feet, then, by referring to Fig. 60, we show to 

 one inch scale the length, run, rise, seat, and 

 plumb cuts for the hip and common rafters as 



