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The try square 379   The T square 379   Various methods of testing squares 379, 380   Bevel squares 380 Bevel Protractors 380 Hexagon Gauge 381 Straight Edge and its applications 381, 382   Winding strips and their application 382 Surface Plate or planimeter 383 Templates for curves 384 Wire Gauges, notch 384   Standard gauges for wire, &c.

The square s is placed in the position shown by full lines pressed firmly to the edge of the surface plate and a fine line is drawn with a needle point on the face of the surface plate, using the edge of the square blade as denoted by the arrow c as a guide.

For some purposes, as for marking out work on a surface plate, it is better that the square be formed of a single piece having the back and blade of equal thickness, as shown in Fig.

Before the finishing cut is taken, the plates or screws holding the surface plate should be slackened back a little so as to hold them as lightly as may be, the finishing cut being a very light one, and under these circumstances the plates may be planed sufficiently true that one will lift the other from the partial vacuum between them.

The Whitworth surfacing straight-edge, or long narrow surface plate, is ribbed as in Fig.