What is a dull weitlaner retractor?

A Weitlaner Retractor is a surgical instrument used for holding wounds open so the surgeon can do repairs below. It has a scissors grip with a ratchet to lock in the desired position. They have 4 prongs on each jaw that can be either sharp for gripping or rounded over OR Dull Prongs. The Dull Weitlaner would the ones with the Rounded Over prongs.