Hardboard aka Masonite... cheap and replaceable. I also use carpet pad on
mine, more to protect the project than the workbench since mine all have osb
tops.

One thing you'll learn about this group, you can ask a simple question and
get a dozen replies that don't answer your question. :-) But that's what
makes it unique.

Welcome to the Wunnerful World of Woodworkin'

Will