I hadn't noticed the ad, in the Trapper. Looks like it's made of square-tubing, guess a piece of pipe would work as good? It still looks like you'd have lots of drag/resistance on the "lock". ??? I have some small (1" or less) rigid conduit out at the shop, first chance I get I'll cut off a 2" or 3" piece, could cut one end at a 45* angle, (may need a longer "tongue") and see how it works. Was just thinking, could stake both ends of the chain here in the back-yard and hook the dog to the rig, and see what happens. It might surprise me???