Fig. 27.—Two-foot, Four-fold Rule.
Fig. 28.—Zigzag
Rule.
29. Rules.—The two-foot, four-fold rule (Fig. 27) is the one generally used by carpenters. It is made of different grades, the more expensive makes being divided into 16ths, 8ths, 10ths, and 12ths, and having the ⅛“, ¼”, ⅜“, ½”, ¾“, 1”, 1½“, and 3” scales upon them. Although the cheaper rule is just as accurate, it is divided usually into 8ths and 16ths only. The form of rule shown in Fig. 28 is becoming quite popular, as it is longer. Since rules are easily lost or broken, many workmen have a good rule for scaling, and a cheaper one for general work.
30. The try-square (A.) consists of the beam (Fig. 29, a), which is generally of metal-lined wood, and the blade (b), which is a thin piece of steel.
(B.) Too much care cannot be exercised in the selection of this tool, as one which is not perfectly true may cause much trouble. To test a square, hold the beam against a perfectly straight and square edge of a board which is wide enough to allow a knife line to be made the entire length of the blade. Then turn the square over, the other side up, and, holding the beam against the same edge, move the blade to the line. If the jointed edge of the board and the square are perfectly accurate, the knife line and the edge of the board will perfectly coincide.
Fig. 29.—Position of Try-square in Squaring an Edge.
Fig. 30.—Use of Two Try-squares to See if Piece of Wood is “Out
of Wind.”