ABC OF THE STEEL SQUARE 



31 



der the graduation mark 18 and 12 feet is found 

 to be the board measure. If 13 feet long and 7 



inches wide, find 13 in the scale 

 under the 12-inch graduation and on 

 the same line under the 7 -inch grad- 

 uation will be found 7 7-12 feet 

 board measure. If the board is 

 half this length, take half of this 

 result; if double this length, then 

 double this result. For stuff 2 

 inches thick double the figure. 



In this way the scale covers all 

 lengths of boards, the most common 

 from 8 feet to 15 feet being given. 



This company also manufactures 

 a square that is "blued," or appar- 

 ent;!/ oxidized, with all the figures 

 on it enameled in white. This i^ 

 really a handsome tool, and the 

 white figures on a dark blue ground 

 enable the operator to see what fig- 

 Fig. 14 ures h e ' ls looking for without waste 



of time and straining of eyesight. 

 The bridge builders' steel square, which is 

 illustrated in Fig. 14, is also made by this com- 



