Fig. 4.
Sometimes there is a brass slide, to add to its length when necessary, and sometimes it is hinged so as to fold up again. If you want one for your box, you can get it so made, when it will go in nicely. It is 2 feet long—1 foot on each side of the central joint. A foot is 12 inches; the whole rule, therefore, is 24 inches. Now, you will see that each of these inches is divided by short lines into eight equal parts, called eighths; at the second, the line is rather longer, this being a quarter of an inch; at the fourth, there is a still longer line, this being the half-inch; then comes another eighth, then the three-quarters, another eighth, and the inch is made up,—eight-eighths being equal to one whole inch. Very likely you will find one edge of the rule, or sometimes only one inch, divided into smaller parts, which are sixteenths, or half-eighths; and sometimes, but not very often, divisions still smaller are used, which are half-sixteenths, or thirty-seconds, because thirty-two such divisions make the complete inch. Three feet make one yard, but carpenters always reckon by the foot and inch, and by eighths and sixteenths of an inch. In some trades the inch is divided into a hundred parts, and work is measured up and fitted so carefully, that it would be considered faulty if a mistake of less than a thousandth of an inch were made; but you will not yet understand how it is possible even to measure so very small a quantity. You should certainly learn and understand how to measure with a common two-foot rule, and when you can add one to your box of tools, do so.
Now, let us examine the tool called a square, without which the marks could not readily be drawn as a guide for the saw, where the strip of board is to be cut to make the sides and ends of the proposed box. Here is a drawing of one (Fig. 5).
Fig. 5.
Fig. 6.
It is a handle and a blade, like a knife half opened, the one being fixed exactly square, or at right angles with the other. The blade is thinner than the handle, and when the latter is placed as in Fig. 6, a line marked across the board against the edge of the blade will be, of course, square to the side, so that when cut off, the piece will be like the end of Fig. 6. This is not the shape which the sides of boxes generally have when made by small boys, because they have not a square, and do not know how to work properly. Nevertheless, if one end of a board is cut square, you might get the piece right by measuring the same distance on each side (say 10½ inches), and drawing a line across from point to point, as a guide for the course of the saw. But, then, as it is absolutely necessary that the end of the board should be square to the side, to do this you had better get a proper square at once, and learn how to use it. You will, indeed, find this tool most necessary for all kinds of work, and you will be quite unable to do without it, even though you only have, besides, a knife and gimlet.