Gumbo I rely on a principle that I don't fully understand, If I remember a little about my high school science class I think they called it gravity. In extreme situations they can and do slip, but then so do the others. Its just a quick cheap way of getting the trailer off the ground and the blocks can be used for leveling as well as jack pads. I personally use aluminum ramps with groves that accomodate a matching chock. I think these were carried by Camping world about 10-15 years ago. The only place I have found them has been at flea markets at the bigger rallies. Best of luck. Rick
Keep the shiny side up.
WBCCI # 348
Past Region 3 President
Past President Tidewater Unit 111
Rick Bell in "Silverbell"