The AF37FN is a flush-mount panel board enclosure, 37.500 in tall by 20 in wide, from the AF family. It ships with trim and a nameplate, ready for a cutout in a finished wall or partition. The NEMA 1 rating means it's for indoor use only — general-purpose protection against contact with live parts and falling dirt, no gasket for washdown or dust.
Flush mounting means the front face sits level with the surrounding wall surface — the trim covers the cutout edge. Plan for a rough opening that accommodates the 37.500 in height and 20 in width, plus clearance for the mounting brackets and conduit entries. NEMA 1 enclosures typically accept knockouts on the top, bottom, and sides; verify the knockout pattern on the actual unit before laying out branch circuits.