A ziz-type ledge conveys tumah even if its width is minimal; whereas gizrah- and gavlis-type ledges [convey tumah] only if they are a handbreadth wide. What is a ziz-type ledge? [A ledge] whose face extends downward. And [what is] a gizrah-type ledge? One whose face extends upward. When does a ziz-type ledge convey tumah even if its width is minimal? When the ledge is three rows of stones, which is twelve handbreadths, above the doorway. [If the ledge] is higher, it spreads tumah only if it is a handbreadth wide. Ornamental archways and awnings spread tumah if they are a handbreadth wide.