the simplest form is a "straight" comb (a), which is the default form seen in all traditional rifles with iron sights. the "monte carlo" comb (b) is commonly found on stocks designed for use with scopes, and features an elevated comb to lift the cheek higher, while keeping the heel of the stock low. if the elevated comb is of a rounded dome shape, it is often called a "hogback" comb. a "cheekpiece" (c) is a raised section on the "side" of the stock, which provides a more comformed support for the shooter's cheek. there is some confusion between these terms, as the features are often combined, with the raised "rollover" cheekpiece (d) extending to the top of the stock to form essentially a high monte carlo comb.