A closer look at the first pin to be slotted. The excess beyond the slot will be trimmed off. Flats were milled on the head to allow for assembly; these must fit into the truck bolster from the bottom, and the clearance is a bit tight, due to a reinforcing lip cast into the bottom of the cast-iron bolster. The pin is a very sloppy fit in the bolster holes (both frame and truck), as its only function is to keep the trucks from separating from the locomotive in case of a catastrophic derailment (roll-over). This must make it more convenient for the wrecking crew to gather up the wayward pieces.

Photo by Rick Brigger