So if you need to tie something down to the floor of a trailer, is there a product out there that's recessed but doesn't get in the way of casters? Almost all the tie-downs I see are either a surface mount ring (bump protruding from the floor) or they've got a big hole in the center of the ring for the caster to trip on (like a pothole in the road). Or they are designed as pulls and aren't heavy enough to use as a tie-down point. The ones I've found that fit the bill seem like they are waaaay overpriced.
Looking for something that's flush mount, but doesn't have open holes to get in the way of casters, cause uneven footing, or fill with debris, and less than $20 each.
If money was no object, I might get some of these:
http://www.monitormarine.co.uk/helicopter-tie-downs-t45-units.php -- I fear to think of what those must cost.