The Rockwood 2842 automatic flush bolt Set:

is for Metal Doors Fire Rated up to and Including 3 Hours, and comes non-handed. Rockwood Commercial Automatic Flushbolt Set Top And Bottom, 2842 requires a low closing force and has an override feature that prevents damage to doors or bolts if bolt heads are blocked from entering strikes. The Rockwood 2842 has a Thermal lock that automatically locks the inactive door under high heat conditions due to fire. Rockwood 2842 flush bolt set can be used with the Rockwood 570 Dust Proof Strike. See Spec's