I use these rusty old metal ramps with little extensions, and chock a wheel at the opposite end of the car. Haven't died yet... They seem very strong and sturdy, I've used them hundreds of times, and they must already be quite old...
The upright supports are angle steel, quite thick, butted and welded into angle steel on the bottom, and welded to the bottom of angle steel at the top, no way its going anywhere...
Those red ramps earlier in the thread worry me though with the little bars on the sides which seem to be welded (poorly) onto the sides of the ramp... Pretty crap!