Here are a couple of them - and the one that we use. First of all -- how others solve the problem.
This is the most "traditional" method. It's probably not the best for towing on the highway, but is fairly low and therefore easy to load at the end of the course - or unload in line:
Then there's the kind that holds the front wheel only. I don't care for these because turning is difficult -- the bike wants to lean over when the towing car turns, stretching the away-side strap and sometimes even bending the bars/relocating the handlegrips:
So after a few years of trying and thinking and modifying we ended up with this. It's not only easy to load and doesn't subject the bike to any twisting or bending -- but we can remove the wheels and then fasten the trailerette (gotta call it something) to the floor of the big trailer. That done -- we load a bike onto it for transport. the result is that we lose NO space in the big trailer just to carry the little trailer. It's got a front wheel chock to hold the bike in place while the rear is getting strapped down, and with ground clearance of less than an inch - we don't need a ramp.
Later - -