A serrated shield is a round heavy steel shield, which has a sharpened, serrated edge 3/4 of the way around the outside. (The unsharpened section is designed to be the part held close to your arm and body when defending.) If you are proficient with a serrated shield, when you use it for a shield bash, instead of the usual damage the shield deals 1d6 slashing damage (1d4 for serrated shields designed for Small creatures) and threatens a critical hit on a natural attack roll of 19–20.