Use a 3/4 inch cable or bigger with a rubber coat and suspend it between two axels and put into the ground. How far you want to bury and how tight you want to suspend it will be up to you. No slack and buried deep will have the cable too tight to the ground with not a lot of room if any for the chain to move back and forth. You can almost use anything to attach the chain by just keep in mind it will need maintenance as the dirt build up will grow from the chain moving back and fourth. I raked mine every day when I cleaned up shit just to make sure the dogs movement wasn't restricted or that he didn't have to put too much extra effort in sliding the chain across.