cribbing for under TC jacks

I use 4x6 wood blocks, about a foot long each, under my camper's jack legs, because the jacks are too short to reach the ground. I stack them 3 high to load/unload the camper from 4x4 truck. They also work fine for using the jacks to stabilize the camper/truck when parked.

If all you're looking to do is take the weight off the truck's suspension, why not just use a hydraulic jack under the receiver hitch? Most jacks can lift the rig up about 6 inches which, at least on my Ram dually 4x4, is more than enough to unload the springs. The rig is still very stable this way. I use a 8x8 block of wood for the jack to sit on so it doesn't sink into the ground. Quick and easy and you can be ready to go in less than a minute, no need to crank up the camper jacks.

I've stacked 8x8x18 cinder blocks under each leg so I don't have to lower the jacks all the way to the ground in order to relieve pressure off of my truck suspension when parked in the driveway. They are heavy, not easy to move, but they are very stable, not likely to wobble and tip over like a log or timber.

I use 4x6's by 14" one in each corner. Carry them with us when we go camping to stop the movement of the camper a lot easier than letting the jacks up and down all the way.

I use 6 composite pallets with roof timbers laid across the top to get plenty of width to fully support the camper (only during winter storage when the camper isn't in use).

I use 12- 14" diameter logs that are about 14" tall at each corner.