there right at the very end as he drops the trailer back down, you can see the "cable" ran up from the top of the L raceway... its right at point he reaches in to move the leg. the cable shines just for a moment.
at first i thought it was just a generic "bottle jack" like setup. power up. but goes down under its own weight. and was just using the crank vs a handle ya gotta go up and down on.
not so sure i like the free wheeling of the handling, i think i would end up getting tangled up in the handle. or having a few broken writs/hands/fingers from getting caught up in it.
regardless well thought out! with some ingenuity put in to it!