Doors are rated by Underwriters Laboratories for 1-1/2 hours, "B" label in walls, and by Warnock Hersey for 3 hours in ceilings and 2 hours in walls. Door should be utilized when providing access in fire rated walls and ceilings. Doors have heavy-duty spring closures to ensure positive latching when panel closes. Door is fabricated from 20 gauge, galvannealed steel with a prime coat finish. Door panel is provided with 2" of insulation in a sandwich type construction. Frame is fabricated from 16 gauge, galvannealed steel with a prime coat finish and provided with masonry anchors and bolt holes. Hinge is a fully concealed and mounted on the long side of the rectangular door panel. Exterior Latch is a dual purpose lock that features a knurled knob and key operation. Both are provided at time of shipping. Interior Latch Release Slide is included enabling door to be opened from the inside.