Steps.—Steps are built up with two sides of the required height, about 5 inches wide and 1 inch thick; the top and bottom are sawn to a bevel so that they stand inclined.
The steps, which are grooved into the sides and fixed with screws, are about 6 inches wide by 11⁄2 inches thick, and increase slightly in length as they descend. This increase adds to the stability of the steps as the width of the base is increased. The distance between each step is from 7 to 9 inches.
At the back of the top step two legs about 21⁄2 inches wide by 1 inch thick are secured by strong flap hinges. The legs are framed together by two cross pieces, 3 or 4 inches wide and 1 inch thick.
The back legs, by opening out on the flap hinges, enable the entire framework to stand upon an even surface. To prevent the legs opening too far, they are connected to the sides of the steps by cords.
Cripples.—The simplest form of cripple is shown on [fig. 66], which sufficiently explains the design.
This cripple forms a fixed angle with the ladder, which, in order to keep the platform level, can be laid only at one slope against the wall. The defect is removed if the cripple is hinged and fitted with a quadrant and pin, as shown on [fig. 67]. The platform in this case can be kept level by adjustment irrespective of slope of ladder. The bracket should be long enough to carry a platform three boards wide, but as a rule it carries two.
Fig. 66
Fig. 67