Backed: Letter is routed out of aluminum (typically) and backed with acrylic. There is a small reveal along the edge of the aluminum where the letter has been cut out of the face of the sign.
Flush: Acrylic is CNC routed then placed behind the routed aluminum panel and secured. The acrylic has a shoulder routed to a depth that allows the face of the letter to be flush with the face of the aluminum.
Push Through: Similar to flush, where the acrylic is CNC routed, however, the thickness of the letter is much greater than the aluminum so that the letter protrudes from the plane of the aluminum face. The thickness of this acrylic is dependent on the amount of push-through you’d like to reach. Typical depths of push through letters range from ¼” — ¾” on average. Push through lettering also allows for vinyl or laminate overlays on the letter for achieving a color with a halo illumination.