Northern Prairie Wildlife Research Center
All of the predator guards shown below serve the same purpose--to keep predators such as house cats, raccoons, and snakes from scaling the support post to your nest box or feeder. Wood posts are the easiest for predators to climb because they provide a rough surface with a good grip. Metal pipes or posts are less likely to be climbed successfully.
Materials to build predator guards can be made from tin, sheet metal, aluminum, or heavy plastic. A good source of cheap sheeting is often a newspaper office. Aluminum sheets are used to make the impression to print the newspaper and are recycled afterwards.