i have used BED BOLTS in the floors of trailers for quite a few years
https://www.bedbolts.comthey are designed to fit between the ribs in the floor of a pick up so their tops will clear anything loaded on the floor
i simply pull(wrench 'em down) flush w/ the plywood/plank surface for easy loading when knot in use
they come w/ plastique plugs for the hole when knot in use

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w/ the internal threads being 3/8" you can bolt anything you wish to them
i run 4ea down each side and the center of a 12' trailer
Tractor Supply sells knock offs
sw