The drawing associated with this model is an excellent one, giving a good practical application of geometry to actual work.

After drawing the outline of the plan, draw a square on one end of it equal on its side to the breadth-of the wood. Draw the diagonal of the square and proceed to make lines parallel to it, and at a distance of 5/8 in. from each other.

Side elevation. Fig. 105.

From Series IV. ' Hand and Eye Training' Cards, by kind permission of Messrs. Cassell & Co.

To do this in the way which will be found most suitable to actual work, set up two parallel lines, a a', from the diagonal and at right angles to it. Mark off 5/8 in. on these, and join the marked points. Mark off all the lines in this way.

The elevation should be projected from the plan. Isometric projection need not be used in this case.

Having drawn the exercise on paper, the wood should be marked out for sawing.

At the end a square should be made as in the paper drawing, but as the end is probably not quite at right angles to the edges, a line which is perfectly square is set out with the try-square at a little distance from one end, as at ab in fig. 105, and this line is now considered, for the purposes of measurement, as the end of the exercise. Finish the marking as in the paper drawing.

The lines should be cut with the chisel, making use of the blade of the try-square as a straight-edge.

A carpenter would use a bevel for this purpose, but the liability to fall into the error of measuring the distances along the edge of the wood, instead of on right projectors from successive cut lines, is much greater when this tool is used than if the edge of the square is taken. Moreover, the square is now in a novel position - the stock no longer rests against the wood, and it is slightly more difficult to hold in a given position, thus giving the pupil more knowledge of the use of the tool.