Front Runner Wolf Pack chock

These chocks will fit under the Front Runner Wolf Pack (not Pros) corners to hold them from shifting. They mount to a Front Runner Slimline II rack, but could probably work with any kind of tray. The nut goes in the top and should be a press fit, the bolt goes in the track and you thread them down. Make sure you print a few as a mirror on the long edge, so they work on both corners. 

I typically use 2 per Wolf Pack on the shorter edge.  These allow you to use one stratchet or strap to hold down the Wolf Packs instead of multiple like with the Front Runner Wolf Pack mount kit. I've had these through some rough forest roads and they've done great. If it doesn't line up, unscrew it until you can slide it out of the slot and turn it a bit then slide it back in and see if that helps. 

I believe the hardware is 5/16th stainless. I will update with better measurements. I have not tested with the Wolf Pack Pros, but they should work from what I have seen of them. 

I also have an untested prinsu rack version. Message me if you're interested.