Generally, NO, Hart & Cooley does not want sheet metal screws used in the assembly or installation of our Type B gas vent. Screws can generate serious noise problems that adversely affect the perceived performance and value of our product. They are not needed to secure a connection because the connection is already UL listed as it is designed. However, there are exceptions that we allow screws and that is for connections of single-wall pipe to the B-vent. Fold back the outer wall locking tabs that can act like an access "door" to secure the aluminum inner wall and single wall pipe together using 1/4" stainless screws.