The lower extremities of principal rafters are sometimes secured in cast-iron shoes with cottered joints, as already explained in Part I. Cast-iron heads are seldom used for large roofs.

Illustrations of cast-iron shoes are given in Part I., also in Figs. 319, 320, 321, Plate VI., and in Figs. 328, 329, 330, Plate VII.

Fig. 298.

Simpler joints are formed by the use of flat wrought-iron plates, to which the parts to be connected are bolted or riveted. when the principal rafter is of two angle irons one plate may be inserted between them, as in Figs. 298, 299, which are details of the joint A of the roof, Plate XI, and of Fig. .367, Plate XII. When the principal rafter is of T iron then two plates may be used, one on each side of the web, as in Fig. 337, Plate VIII., and Figs.350, 351, Plate X.

Fig. 299.

Fig. 300 is a simple joint with plates connecting the foot of the principal rafter with a tie of T iron.