A strap at the foot of a principal rafter is intended to form an abutment for it, in case the end of the tie-beam should fail. If the strap be put too upright it will become quite loose when the roof settles, instead of forming an abutment; and as it is intended to prevent the Lot of the rafter sliding along the tie-beam, an oblique position, as shown by Figs. 144 and 155, will be the most effectual. Straps of the same size as are used for the king post will be sufficient. In bolting on straps they ought to be drawn tight. Price recommends square bolts for this purpose. He says, " If you use a round bolt, it must follow the auger, and cannot be helped; but by helping the auger-hole, that is, by taking off the corners of the wood, you may draw a strap exceedingly close, and at the same time cause it to embrace the grain of the wood in a much firmer manner than a round pin." *

Fig. 155.

Sometimes a bolt put through square from the back of the rafter is used with cross plates at the head and nut. Fig. 144 shows this method, the dotted lines representing the bolt.