Connecting rods are usually made of steel cast in a mold at the foundry. The rough molded rods were then inserted while still hot into a stamping mill, which shaped them with tapered ends and reinforced edges. They have thicker, rounded ends with holes for the axle cranks. They taper slightly from end-to-end to cut down on weight, and have channeled straight sections, again for weight reduction—as well as strengthening. They are mounted on the axle ends with some minor tolerance (the hole is slightly larger than the crank), and fastened in place with very large Cotter pins.