Within the industry, the terms "flush mount," "surface mount," and "recess mount" can mean different things. This leads to confusion when selecting perimeter lighting for your apparatus.

Surface-mount light heads do not require a body panel cutout for installation. The only holes in the vehicle body that are needed for installation are the screw holes and a wire pass-through hole.

Federal Signal uses the terms "flush mount" and "recess mount" interchangeably. Flush- and recess-mount light heads require a body panel cutout (in addition to the screw holes) so that some portion of the light gets recessed into vehicle body during installation. The portion of the light that still protrudes from the vehicle body typically will have some sort of flange or trim ring to make the light head look flush with the body.