2. The lower extremity of the thigh piece has cut in it a central mortise into which fits a vertical plate, prolonged upwards from the middle of the leg piece. The bolt passes through this artificial tibial spine and through the two sides of the mortise in the thigh piece. If the hole in the tibial spine through which this bolt passes is square the hinge works securely ([Figs. 34 to 36]).
In this form the axle turns with the leg, in the first form this is also possible. But most often when the forked attachment is used it is fixed to a leather thigh piece, and each end of the fork is jointed independently to the corresponding end of the lateral steels of the thigh piece, without any complete transverse bolt. It is then the fork that revolves around these two joints.
Figs. 31 to 33.—Fixation of the stirrup of the leg (Fig. 31) by a transverse bolt (Fig. 33), the aperture for which in the thigh piece is seen in Fig. 32. Double lock (Fig. 32).
Figs. 34 to 36.—Attachment by mortise and tenon, with a bolt, square in section, passing through the knee. Single lock on the outer side.
If there is a complete transverse bolt, the joint can be securely locked by a single lock at one of its extremities (at the outer extremity) (Figs. 36 to 39).
If there are two lateral joints the single lock is insufficient, both joints must be fixed at once; unless this is done, that which is not fixed has a certain amount of play and is strained.