A straight edge to level walls and buildings should be made of 1 1/8"x8"xl6' of edge grain lumber to prevent warping. Straighten the bottom of the straight edge. Measure to the center of the board and from this mark measure 18" on either side. From this point draw a line to the end 4 1/2" from the bottom and up the taper line and gauge the same width from the bottom in the center of the board to the tapered lines. Cut a handhold in the center 1 1/4" wide by 4" long, leaving 1 1/2" on the top edge. Set a true level on the top edge. Level the board, reverse the straight edge on the same bearings, if the bulb centers the straight edge is true, if not, plane off the high point on the top edge until it reverses the same. The plumb straight edge should be 4 1/2" wide and the length of the height of upper plate. Put a 7/8 block on each end to keep the board clear from any timber that may be bowed. Make perfectly straight, and see the ends measure the same width.

The straight edge to set the jambs, line cabinet work, etc., straighten and gauge the same width the entire length. That in straightening a jamb, it can be plumbed at the same time. To test a straight edge, lay it on the floor, draw a line reverse the board end to end, draw another line. If the lines are parallel, the edge is straight, if not, plain the defects until it reverses the same. (Fig. 68.)

Fig .68