The gauge is used, as was described in Lesson II (Use Of The Gauge)., to make lines on the side or edge of a board parallel to the grain. The try-square is used to guide a pencil or knife in making lines at right angles to the grain. It consists of two parts, the beam and the blade, as in Fig. 51.

Fig. 51.

Problem J. Use of Try-Square with Pencil. - Take a board

Fig. 52.

8 in. X 1 1/2 in. X 7/8 in. Hold the rule on it, as in Fig. 52, and with a fine pencil-point, operating as in the measurement lesson, place points on the wood at every inch graduation of the rule.

Hold the try-square as in Fig. 53, using the left fore-finger to press the blade firmly to the face of the board while the thumb and remaining fingers hold the beam firmly against its edge. Place the point of the pencil in one of the points which it has made on the board, carefully move the try-square against it, raise the pencil, and with it draw a fine line across the board close to the blade of the try-square.

Fig. 53.

Fig. 54.

In doing this the right hand should grasp the pencil as though writing with it, and the pencil should incline to the right just enough to bring the left side of its cone of sharpening vertical, as in Fig. 54, which is a front view of the pencil, try-square blade, and board. Draw the pencil only once.

Turn the board so as to bring its front edge uppermost, and in a similar manner draw a line across that edge, as in Fig. 55.

Fig. 55.

Repeat this process on the second side, and lastly on the second edge, when a line is squared entirely around the board and should meet its starting-point, as in Fig. 56.

Fig. 56.

In Fig. 55 the right hand holds a knife instead of a pencil, and in that respect illustrates Problem II., instead of Problem I.

Square lines around the board through the other points. The effort of the pupil must not be to fill the board with lines, however, but to make perfect lines.

Problem II. Use Of Try-Square With Knife

Lay the rule on the board again, as in Fig. 52, and with a sharp knife point, operating as in the measurement lesson, make impressions in the wood at half-inches.

Use the knife as the pencil was used in Problem I., and square lines around the board passing through these half-inch points. The knife, like the pencil, must be inclined to the right, just enough only to allow its point to cut the wood close to the try-square blade. The knife blade must furthermore be turned as in the plan view A, Fig. 57. If it is turned too much to the right, as at B, it will move away from the try-square blade in the direction of the dotted lines. If turned too much to the left, as at C, it is liable to be dulled as it slides along the try-square blade, and there is danger of its pushing the trysquare blade out of place, unless the grasp of the left hand is very firm. This same danger of the try-square slipping is imminent, if at any time the right hand presses the knife too hard against square.

Fig. 57.

In Problem I. instructions were given to draw the pencil but once in making any given line. This is to avoid wearing away the pencil and blurring the line. The knife, on the contrary, needs to be drawn twice, first lightly to locate the line, and second heavier to deepen it, as each line should be deep enough to be seen when held at arm's length, or should easily arrest the finger nail when drawn across it. After squaring any given line around the board, rest a few seconds before commencing another. Otherwise the muscles will tire and success be impossible. A board filled with pencil lines at every inch and knife lines at every half-inch will appear, as in Fig. 58.

Fig. 58.

If success is not yet attained, practise the making of lines at every 1/4 in., and, if necessary, at every 1/8 in.