Stall guards—webbing or chains that stretch across an open stall door—can maximize the fresh air in a horse's living space and allow him to observe the activity around him. These benefits do come with risks, however, and you'll need to take a few precautions to ensure you are using the stall guard safely and your horse stays contained.
For starters, install every stall guard according to the manufacturer's instructions. Use the hardware sent with the stall guard, unless you're confident you'll be upgrading to even sturdier attachments. Pay attention to recommended heights for installation, but if your horse is particularly large or small, a standard stall guard may not be appropriate. As a general rule, hang the guard so its center aligns with the center of your horse's chest. If you have any suspicions your horse can step over or slip under the guard, look for one of a different height.
Once you've got the guard installed, test its integrity. Pull on it as hard as you can from both directions. Sit on it. If the hardware pulls from the walls or stitches pop, it won't stand up to a horse leaning on it.
Finally, regularly check the security of the guard. Horses who lean across guards to socialize with passersby can gradually pull hardware from the wall. Repeat your "pull tests" regularly, and give the screw eyes another turn to tighten them when necessary. If the wood around the hardware splinters or becomes less "grippy" than it used to be, you may need to raise or lower the guard to ensure a stable installation or replace the door frame entirely. Also check the snaps to ensure they open and close properly.