Page:International Library of Technology, Volume 53.djvu/17

2 the wood and allow it to be controlled by the cleats, at the same time leaving the longitudinal strength nearly unimpaired. In order to provide a perfectly smooth working

edge, for the head of the T square to slide against, a strip of hard wood is let into the short edges of the board, and is sawed through in several places, in order to allow for the contraction and expansion of the board. The cleats also raise the board from the table, thus making it easier to

change the position of the board. When in use the board is placed so that one of the short edges is at the left of the draftsman, as shown in Fig. 2.

. The T square is used for drawing horizontal straight lines. The head A is placed against the left-hand edge of the board, as shown in Fig. 3. The upper edge C of the blade B is brought very near to the point through which it is desired to pass a line, so that the straight edge C of the  blade may be used as a guide for the pen or pencil. It is evident that all lines drawn in this manner will be parallel.