6. The right-hand portion of Fig. 7 shows another method of accomplishing the same result, and illustrates how the triangles may be used for drawing a rectangular figure, when the sides of the figure make an angle with the T square such that the latter cannot he used.
Let the side cd of the figure be given. Place the long side of the triangle B so as to coincide with the line cd, and bring the triangle A into position against the lower side of B, as shown. Now, holding the triangle A in place with the left hand, revolve B so that its other
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short edge will rest against the long edge of A, as shown in the dotted position at B'. The parallel lines ce and df may now be drawn through the points c and d by sliding the triangle B on the triangle A, as described in connection with Fig, 6. Measure off the required width of the figure on the line ce, reverse the triangle B again to its original position, still holding the triangle A in a fixed position with the left hand, and slide B upon A until the long edge of B passes through e. Draw the line ef through the point e, and ef will be parallel to cd. The student should practice with his triangles before beginning drawing.
