The _try-square_, Fig. 200, which is most commonly used for measuring the accuracy of right angles, is also convenient for testing the width of a board at various places along its length, for making short measurements, and as a guide in laying out lines with a pencil or knife at right angles to a surface or edge. The sizes are various and are indicated by the length of the blade. A convenient size for the individual bench and for ordinary use has a blade 6" long. It is also well to have in the shop one large one with a 12" blade.
[Illustration: Fig. 203. Using the Try-Square.]
[Illustration: Fig. 204. Scribing with Knife by Try-Square.]
In testing the squareness of work with the try-square, care must be taken to see that the head rests firmly against the surface from which the test is made, and then slipped down till the blade touches the edge being tested, Fig. 203. The edge should be tested at a number of places in the same way: that is, it should not be slid along the piece. The try-square is also of great use in scribing lines across boards, Fig. 204. A good method is to put the point of the knife at the beginning of the desired line, slide the square, along until it touches the knife-edge; then, resting the head of the square firmly against the edge, draw the knife along, pressing it lightly against the blade, holding it perpendicularly. To prevent the knife from running away from the blade of the try-square, turn its edge slightly towards the blade.
The _miter-square_, Fig. 201, is a try-square fixed at an angle of 45°.
The _sliding T bevel_, Fig. 202, has a blade adjustable to any angle. It may be set either from a sample line, drawn on the wood, from a given line on a protractor, from drawing triangles, from the graduations on a framing square, or in other ways. It is used similarly to the T-square.
[Illustration: Fig. 205. Winding-Sticks, 12 inches Long.]
_Winding-sticks_, Fig. 205, consist of a pair of straight strips of exactly the same width thruout. They are used to find out whether there is any twist or "wind" in a board. This is done by placing them parallel to each other, one at one end of the board, and the other at the other end. By sighting across them, one can readily see whether the board be twisted or not, Fig. 206. The blades of two framing-squares may be used in the same manner.