I've use ramps for years as well. Like anything that's designed to work with a heavy load, it's something to be respected. FWD cars can climb a ramp on pretty much any surface since it's clawing it's way up instead of pushing.

What I do in the garage since the concrete is slick is simply put down 2 2x4's between the ramps and the wall so they can't scoot.

Speaking of accidents, one time I had a car on ramps. I had it in neutral and the e-brake set, running the engine looking for a leak or something. The owner walked around front, bent over with her hand on the bumper to see what I was doing and that was enough to cause the car to start to roll back off the ramps. Appearantly, the e-brake was useless... Anyway, I'm laying on the ground under the side of the car with my hips in the path of the oncoming tire. Since there was no way I could get out in time, I sucked in and turned my face sideways to hopefully keep from getting it squashed. I also pulled my arms back flat to the ground in an attempt to get as skinny as possible.

Here's where the miracle happened... The flashlight I was holding (cheap plastic thing as I remember) got stuck on the undercarriage as I was pulling it back. As the car rolled down the ramp, the flashlight planted in the ground and acted as a wedge - actually raising the car body. The wheel bounced into my hip (not too pleasant) and the car came to a stop with the flashlight perfectly straight up and holding the car body off of me. I couldn't even move enough to scootch out so the girl had to drag me out by me feet...

Moral of the story - always block the tires when using ramps...

__________________
-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250