For anyone to give you a detailed answer you will need to give us more info. ie; what sort of trailer are you needing ramps for? is it a 10ton agri plant trailer or a 2ton ifor flatbed?
What are you going to be running up the loading ramps? a lawnmower or a 5ton 360 excavator?
On the scaffold plank theme it works well until you find the planks are basically stacked to make a solid ramp! Really depends of what trailer and load local agri plant lads have some really nice alloy ones but there a very complex arrangement of profiles to give strength for 15T but still light enough to lift.
I have used a couple of lengths of cable ladder with ply inserts to good effect for light cars onto car trailer (borrowed trailer from mate but he forgot to stick ramps with it!)
Hey ok weight will be for a road motorbike not sure of exact weight needs to be about 2 and half meters long. Going on to a 1ton trailer.
Iv got some ange laying around was going to just weld that with runner. But was going to use that for the runners on trailer not sure wha to use for that either. Going to get or make soe motorbike wheel chocks but iv seen people use small box section for runners still in the planing stage.