A protractor is a semi-circle of brass or of German silver and it is divided into 180 degrees—since it is half of a circle and there are 360 degrees in a circle. You can buy one for a quarter.
By placing the edge of your rule in the center of the straight edge of the protractor and laying it on any one of the lines—they are numbered from 0 to 180—you will find the number of degrees the edge of the rule is from the horizontal.
Fig. 47. the t square and triangle on the drawing board
The T square is laid with the head, that is the short thick piece, against the left hand edge of the drawing board which brings the blade, that is the long thin piece flat on and across the board. The triangle is placed against the straight edge. The triangle is laid on the board with one of its edges against the blade of the T square as shown in [Fig. 47].
Simple Working Drawings.
—There are two kinds of working drawings that will be of use to you and these are, (1) plan drawings, and (2) isometric (pronounced i-so-met´-ric) drawings and you will find both of these quite easy to do.
Making Plan Drawings.
—Suppose now you want to draw the plans of a box which, let’s imagine, is to be 5 inches high, 6 inches wide and 8 inches long. The first thing to do is to draw out a view of the bottom, which also serves as the top since they are alike, and you will have a rectangle like that shown at [A in Fig. 48], and mark the dimensions on it, that is, the width and the length of the box. This you do by running a couple of arrows in each direction and marking in the size.
