[djomlas]

i have the ramps too, i dont think they are teh same brand, but they all the same.
my friend came over to change his oil and one slipped as he was trying to back the car onto them, and car was all sideways and scraped all over the bottom of the right side of the bumper, underneath.

i usually try and place them so that the back end is against something like the grooves seperating diff. parts of concrete,worked great so far.
i also first drive the car onto 2 pieces of wood to get the car a littl higher couse otherwise it scrapes on the bottom of the bumper...weird. but those 2 pieces helped and for some reason no more slippage.

so be careful with that definitely