Dont be so sure of yourself there fella, a rat can and will climb just as well as a squirrel.
Even copper pipe and tubular steel
Yeh, but if it's placed away from the tree trunk hanging freely, on a thin enough chain, it's not going to be able to climb the tree, across the branch and down the chain, and dependant on your feeder, even if it does, it still won't be able to sit there to feed, it would just fall off if you have bell shaped feeders.