Go all over the surface with a sand-paper block, using 00 sand-paper, and shellac the board all over. When dry rub flat with the sand-paper block. Make a final test for any possible inaccuracy, and the board is ready for use.
T square and triangles may be made, but as rubber or celluloid triangles are better in some ways than wood, the former are recommended.
The T square is a very pretty little problem in woodwork, and may be made as follows:
Fig. 207. T square and triangles
The design for the head may be either a or b ([Fig. 207]), a being simply a rectangular piece of hard wood, with two rounded corners; b is laid out as shown, sawed near the line and curved side finished with spokeshave. The straight side should be perfectly straight, as any variation will give horizontal lines out of parallel.
The blade may be of one piece, or built up. A very satisfactory combination is to make the head of black walnut, and the blade of hard maple, with black walnut edges. It will pay to make a special shooting board for this work, and to make several T squares at the same time. This shooting board should be slightly longer than the blade. (See [Fig. 206].)
Gauge a line at a distance x from the edge, equal to the width of 2 inches, and tack a straight strip of wood up to this line as a guide. When the blade has been planed to its thickness of 1⁄8 inch, it is to be placed in space x and planed to width.
To plane a piece of hard wood down to an eighth of an inch, tack it to a pine board with three 1-inch brads. The location of these brads can be such that only one hole will be left in the blade to be filled up afterward. One should be in the position of the central screw over the head, the second at the point where hole h is to be bored, the third at about the centre of the blade. Set these brads slightly below the surface, and dress down smooth.