How do you remove a cleanout plug when the nub for where you put the wrench on has been rounded off?

To remove a stuck plastic drain cleanout plug use a sharp chisel and a ball peen hammer, break up the drain cleanout plug using the hammer and chisel. Be careful to not hit the surrounding pipe and stop to remove pieces of the drain cleanout cover as they are broken. It is important to remove all of the pieces of the broken plug before attempting to install new cover, good Luck.

John

Is it plastic or metal ?

how do you remove a cleanout plug when the nub for where you put the wrench on has been rounded off?

John had the correct answer for both metal and plastic clean out covers, (see image) Good luck, Tom