The choice of face trim depends on both the application and the desired look.
When a siding is used such as wood, cement board, fiber board, vinyl or any other low profile siding the 3/4" x 2 3/4" (SE) Square Edge trim is typically used. The square edged trim is the most common because it matches most house trims which are also square edged.
The brick molding is typically used in brick, stone, or stucco applications, although the 2 3/4" SE trim is sometimes used in a surface mount application on stucco. Kimball Design recomends the use of the 1 1/8" x 2" brick mold for most brick mold applications where the vent trim is set into the finished wall. The 1 1/8" (5/4) brick molding is a deeper profile for a more dramatic look.
The face trim is attached to the vent box with galvanized staples and water resistant glue.
When primer paint is ordered the staple holes and wood joints are puttied using a plastic putty and sanded smooth.