ABC OF THE STEEL SQUARE 



85 



under the following conditions : No. 1 hip when 

 not backed, No. 2 hip when backed, No. 3 valley 

 when not backed, No. 4 valle} T when backed. 

 No. 1 is outlined by heavy lines, and sets lower 

 than the others. By tracing the bottom line of 

 the sections down to the seat of No. 1, thence up 

 to the second elevation will show just how deep 

 the notching should be for each rafter. No. 1 

 cuts into the right hand vertical line from the 

 plan, which would make it stand at the right 

 height above the plate, but in order to make the 

 seat cut clear the corner of plate, it is necessary 

 to cut into the center line above the plan. No. 

 2 cuts into the same points as No. 1, but owing 

 to its being backed, the seat cut drops accord- 

 ingly. No. 3 cuts into the center vertical line, 

 avid in order to clear the edges of the plate must 

 cut out at the sides to the left vertical line. No. 

 4 cuts in the same as the latter, but as much 

 lower than No. 3 as No. 2 is below No. 1. 



The outer vertical lines from the plan repre- 

 sent the width of the rafter. Therefore if the 

 rafter be two inches thick, would be one inch 

 apart, and this amount set off along the seat line 

 (or a line parallel with it) will give the gauge 

 point on the side of the rafter. To make this 

 clearer refer to Fig. 53 ; 17 and 9 gives the cuts. 

 Now leaving the square rest as it is, measure 



