It's a tool for gutting and/or skinning a deer in the field to lower its weight to carry it back to camp. Only thing this would really do is make it a bit less messy I suppose, but if you're not an idiot it's not hard to clean a deer in the first place and you wouldn't really need it.
Have you ever gone deer hunting and had to drag a 200+ pound deer out of the woods after tracking it down? It's fucking exhausting and sucks ass, so a lot of people opt to gut it before transport.