Like already stated a chain deflector but I use for a couple other purposes:
1. Easy place to quick link a disposable stake. Why would I do that you ask? Some place along roads I trap on are too hard for stakes, yet are pretty open so I don't want them to have free reign on a drag. I don't like looking for them unless I have too. Why not just long chain to a disposable? Some times I can get a disposable in a few inches and will probably hold but just in case it comes loose the drag is a backup. Usually the long chain itself will allow critters to get off in the ditch out of sight. When I'm talking roads I'm talking two tracks roads on a hunting club.
2. Similar situation but usually in an even more open place like under a highline. Instead of using a disposable stake I use a rebar stake with the top still sticking up drove in at an angle with the top pointed toward the woods. Coon, fox, possum, and bobcats will usually not pull the drag loose but the more visible jumping around coyotes will. With the stake angled toward the woods they will be that direction when they pull it loose and keep going that direction and will be hung up and hiding just inside the woods. At least in a perfect world, but it does work pretty good.
That's actually pretty cool information, thank you.
This year was my first full season and first time using drags. I just wrapped the drag around a small tree/sapling and then wrapped the chain around the drag a couple of times. Or I'd find two trees/sapplings very close and drop it in between the two.