I was looking at different plans for making a workbench that, one day, I will have the space and materials to make. One sets of plans I ran into had a board cut and recessed with a handle.
I have seen lots of bench plans but can't find more than this one using an insert (perhaps insert is a colloquialism?). Sure it makes a wicked paddle but what would the use of this space be?
Image from http://www.shavingsandawl.com/