The front edge of a box installed in a combustible wall must be flush with the finished surface. Which term describes this alignment?

• A. Flush
• B. Recessed 1/8 in
• C. Protruding 1/8 in
• D. Set back 1/4 in

Answer: (A)

Flush means the front edge sits in the same plane as the finished wall surface. When a box is installed in a combustible wall, being flush ensures there are no gaps or protrusions that could compromise the finish, interfere with cover plates, or affect firestop and clearance requirements. So the term that describes this exact alignment is flush—the edge is even with the wall surface. Recessed or protruding descriptions imply the edge is back from or ahead of the surface, and set back implies a specific distance behind the surface, none of which match the required flush alignment.