Here is a link to a thread that offers photos of the above drag system. ^
Great system. I dont know if this was mentioned by sombody else or not but, I have the hunter saftey system harness. If you take the straps off the tree place it around the head of the deer or antlers. There is a clip on the bottom of the vest feed it through and now you can use your treestand harness to drag your deer out. It works great and because its a vest style there is very little upper body or shoulder strain.
I used it to drag my buck out this year 1/4 mile through a cedar swamp without it I would still be pulling that thing.