I'm like most I take a lot of joy when I can build something with what I have without having to buy something. I have racked my brain for several months thinking about this problem. I have a 5' x 10' utility trailer I built from a boat trailer several years ago making it first into a snowmobile then later a utility trailer. I took it all apart three years ago blasted, primed then painted. I replaced the springs, bought new tires & welded some uprights on it for sides. I have always wanted to slide the ramps under the trailer. I could have bought the materials but that's too easy right. I was fortunate many years ago I was doing a commercial trim job & the GC was selling everything he didn't want. I bought about thirty of these shelf uprights & have used some of them over the years mostly for shelves in the shop or inside my work van.
I will be using two on each side of each ramp. These are 6'L & my ramps are 7'L.
I bolted two together giving me a slide channel on each side of the ramp. These are upside down showing the side against the table will be the side I bolt to the bottom of my trailer. I have cross channels 4' apart these will bolt to under the trailer.
This shows the 2"x10" PT wood ramp sitting inside the channels the way it will appear under the trailer.
Now I have to figure a way to stop the ramp from sliding too far inside because these are a foot shorter than the ramp. I think I'll cut some short pieces & add them to the ends & cap the end to prevent. I will have some more pics later showing how I mounted.