The mitre-box, as represented in Fig. 56, is preferred by many, and has the advantage of guiding the saw on both sides of the stuff being operated on instead of only on one. For this reason it will no doubt be considered preferable, by the novice at any rate. It may be about the same length as the other. I may say that the size of the wood being worked is almost the sole guide to the dimensions of any of these wooden appliances; and, where figures are given, they are only to be taken as giving some idea of what is generally suitable. Provided the corners are square inside, the cuts vertical and at the proper angle, little else is required. A roughly made box, if these details are right, is quite as efficient as one put together by means of the finest work. Pine is suitable stuff. Width of each piece may be about 4 inches. Screws will fasten them together, or even ordinary nails. The cross-pieces on top are merely for the purpose of affording support to the others, and may often be omitted without risk if the box is made of hard stuff. A straight across cut may be made in this as in the block. With either box or block the tenon or dovetail saw is used, and not the larger kind.
A wooden square, referred to in a previous chapter, is among the things which may be made by the user Its shape is identical with the small square already shown in Fig. 31 (page 98). The long, thin blade of it is replaced with one of wood fitted into a thicker piece, as in the illustration referred to, or simply nailed on to it This though perhaps of simpler construction, is not so good a form as the other. The essentials, of course are perfectly straight edges and square angles. Dry, hard wood should be selected, and one of an even grain which will not be apt to twist. The thin blade may be of \ in. stuff, 21/2 ins. wide, and 18 ins. long, the other piece being less, but about 1 in. thick. The thin piece will be fastened in a mortise in the other, and be secured by a few screws. The truth of the square can be tested by laying it on a piece of wood, as shown in Fig. 57, drawing a pencil line along its thin edge, and then reversing as represented by dotted lines, and drawing another line either on or close to the other. If the two ruled lines coincide and are perfectly parallel, the square is all right. If, however, there is any divergence of the lines, it will be an easy matter to plane the edge of the square till the error is rectified. To reduce any risk of the square getting out of truth, it will be as well either to polish or to oil it. It can of course be tested from time to time if considered advisable.
Fig. 56 - Mitre Box.
Straight edges are long pieces of wood for ruling or testing purposes, with, as their name indicates, at least one straight edge. This must be really straight, and not merely something near. Any thickness of stuff may be used, but there is no occasion to have it more than of \ in. or \ in. The edge may be tested in a very similar manner to that directed for the square, viz., by drawing a line with a pencil against the edge supposed to be straight, then reversing the piece, and drawing another line. When doing this it will be well to reverse the ends of the straight edge, and not merely to turn the wood over, as any error will then be more readily detected.
Fig. 57 - Testing Square.
Winding strips, the use of which will be found ex-plained in due course, are merely two straight pieces of any kind of wood of exactly equal width, which may be about 2 in. or less, and sufficiently thick to stand on edge. It is sometimes considered better to have the wood bevelled or thinned away to the upper edge, but this shaping is a matter of taste, and can hardly be considered necessary. It is, however, of the utmost importance that the width should be equal in both and uniform, or the strips will be worthless. The length may be from I ft 6 ins. to 2 ft, for the longer they are in moderation the more easily will the errors they are intended to detect be discovered.