Fig. 26b. A TRIANGULAR SCALE
A beginner’s set of drawing instruments consisting of compasses, with pen and pencil points, a ruling pen and a box of leads all in a nice pocket case, as shown at C, Fig. 26, can be bought for $1.25 and these compasses are easier to handle than the one shown in Fig. 14.
Fig. 26c. A SET OF INEXPENSIVE DRAWING INSTRUMENTS
But the chief instrument you need is a protractor, as shown at D, Fig. 26. This is a semicircle of brass, or of German silver, 3¾ or 4½ inches in diameter and costs 10 cents or 40 cents, according to the size and metal it is made of.
Fig. 26d. A PROTRACTOR FOR MEASURING CIRCLES AND ANGLES BY DEGREES
A protractor, as you may or may not know, is used to lay off angles and to measure angles in degrees. The curved part or scale of the protractor is divided into 180 degrees since there are 360 degrees in a circle. The figures start at both corners with 0 so that an angle of any number of degrees right or left can be marked off. Now the lines formed by marking off angles of 30 degrees are the only ones you will have to make for isometric perspective. To do this fasten a sheet of paper to your drawing board with thumb tacks at each corner and draw a straight line across the paper near the bottom. Put your protractor on the edge of the paper and the pencil line exactly as shown in Fig. 27; lay your rule so that its edge crosses the straight part of the protractor at the middle, marked A in the drawing and also on the line of the scale of the protractor marked 30 degrees and then draw a line on the paper along the edge of your rule.