Hinge Pin

Four pins, and that is the whole assembly

Two hinges per door leaf, one pin running through each hinge, four pins total holding both cargo doors on a standard container. There is nothing more complicated behind the swing of a container door than that: a pin through a knuckle, welded to the corner post on one side and to the door on the other, the same idea as a gate hinge scaled up to carry a few hundred pounds of steel.

What changes that simple picture is a detail most people never notice until someone points it out: on most containers, that pin is not meant to come out. It is welded in place or capped so a thief working from outside, after the doors are closed and locked, cannot simply drive the pin out and lift the whole door off its hinges to get around the lock entirely.

Why the pin gets welded shut

A hinge with a removable pin is a shortcut around any lock, no matter how good the lock is. Pull the pin, and the door comes off regardless of what is holding the handle shut. That is a known weakness on ordinary hinged doors generally, and it is exactly why a container hinge is built, and finished, to close off that route before it opens. A welded or capped pin means the only way in through the hinge side is cutting steel, the same problem a thief already has everywhere else on the box.

What actually goes wrong at a hinge pin

Weight is not the issue. A steel door hanging on a steel pin for thirty years is well within what the hardware is built for. Rust is the real wear point, especially on a container that has spent years outdoors: the pin and the knuckle it rides in pick up surface rust like everything else, and enough buildup narrows the tolerance until the door starts dragging on its swing before it ever gets near the locking bars. A little grease at the hinge, worked in with the door open, usually solves it. A hinge that is frozen solid or visibly bent is a different problem, and one worth a call rather than a wrench.