pics - steps down
half folded, the slot, there's a spindle and a bearing that slides in the slot, the curved over bit is deep enough for steps to stay in place when down. Similar curved end to slot to locate steps when up.
and folded away - there's a small bolt with a brass bush for the over centre latches to hold on to
the rungs below the steps give us access when steps are up - an obstacle leapt out and clobbered them.
it took a few iterations to find steps that worked well. I would have liked a little more length when extended. Important is that top step is same step height as all the others. Recently we've developed "hips and knees", I'll probably have to add handles / rail.
They've had a hard life - but then that's what we built the truck for.