/diy/ - Do It Yourself

I need something to cap off the end of a metal rod/bar that is under my desk chair. I just don't know if that "something" exists. This is just a plain straight rod/bar that is .7cm diameter. I tried experimenting with tape and it didn't work, the moment I lean back or get up it eventually falls out of place. I can't weld glue is because it controls the height of the chair and needs to be free moving.