This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
The usual and simple form of cripple is shown at A in Fig. 205. This is set at an angle to suit the required slope of a ladder against the wall. In order to keep a level platform it can only be laid at that slope. This inconvenience may, however, be obviated if the cripple is hinged and fitted with a quadrant and pin, as shown at B. By this means the platform can be made level by adjustment independently of the slope of the ladder. The bracket should be at least long enough to carry a platform two boards wide. Cripples may be fixed to either side of the ladder, and.