Combining Measuring Appliances. To find the hypotenuse of a right-angled triangle when the other two sides are known, use the rule and framing-square, as shown by Fig. 38. Suppose in Fig. 30 the length ab = 5 1/2", and the length ac = 9 1/2"; to find the length be, apply one end of the rule to the 9 1/2" mark on one leg of the square, and bring its edge to coincide with the 5 1/2" mark on the other leg, as shown by Fig. 38. The reading of the rule where it coincides with the 5 1/2" mark, or 10 7/8", will be the length bc. The length thus found will be sufficiently accurate for many purposes. If the distance to be measured is in feet, imagine every inch on the square to be equal to a foot, and read the result in feet.

If the proportions of the triangle are very large, the figure may be drawn at full size on the shop floor, and the extent of each part determined by direct measurement.