Cal-Royal UNIFB820 Universal Automatic Flush Bolts - For Metal & Wood Doors

Double door assemblies have an inactive leaf problem. Someone has to manually throw a flush bolt at the top and bottom of that leaf every time they lock up, and forget it once and the active leaf loses its strike point. The door starts swinging freely or misaligning against the frame. The Cal-Royal UNIFB820 solves that entirely. It's a patented universal automatic flush bolt set, two fully automatic bolts, top and bottom, that engage by themselves when the inactive leaf closes. No manual operation, no forgotten bolts, no misalignment.

What makes the UNIFB820 stand out is that it works on both hollow metal doors and wood composite core fire doors from a single SKU. Most automatic flush bolt sets are made specifically for one door type. This one installs on either, which simplifies procurement on projects with mixed door construction across a building. Browse our full selection of flush bolts and coordinators or view all builders hardware accessories.

How the UNIFB820 Automatic Flush Bolt Works

When the inactive leaf closes, both the top and bottom bolts engage automatically into the floor and header strikes without any manual input. The bolt head is 1/2" round with a 3/4" throw that seats firmly into the strike. The override feature prevents damage if the door closes against a misaligned strike, protecting the bolt mechanism from bending under installation tolerances. The 5/8" vertical adjustment range lets you set the bolt position correctly without removing the door from its hinges, which saves significant time on retrofit projects. A thermal lock activates passively under fire conditions, adding an extra layer of security when heat causes expansion in the door assembly.

UNIFB820 Technical Specifications

The UNIFB820 is ANSI/BHMA A156.3 Type 25 certified and classified under BHMA 4.1.1 Type 25. It's UL Listed for fire-rated door assemblies, compliant with UL10C positive pressure standards and UBC 7-2-1997 codes. The face plate measures 1-1/8" x 2-1/4" with a 1/2" round bolt head and 3/4" throw. Vertical adjustment range is 5/8". The body is steel with stainless steel internal components. The design is reversible and non-handed, compatible with standard ANSI door preparations. It accommodates doors up to 8 feet in height. The UNIFB820 carries a patented design and meets the Buy American Act.

Which UNIFB Configuration Is Right for Your Door?

Knowing which configuration to order before purchasing saves a return. The UNIFB820 includes two fully automatic flush bolts, top and bottom, both engaging automatically when the inactive leaf closes. The UNIFB780 pairs a self-latching bolt at the top with an automatic flush bolt at the bottom. The UNIFB540 pairs an automatic flush bolt at the top with a fire latch bolt at the bottom. The UNIFB930 pairs a self-latching bolt at the top with a fire latch bolt at the bottom.

If your door schedule calls for both positions to operate fully automatically with no self-latching or fire latch, the UNIFB820 is the correct choice. If your fire door label specifies a particular bolt combination, confirm against the series before ordering.

Fire Door Compliance

The UNIFB820 is UL Listed for fire-rated door assemblies and complies with UL10C positive pressure and UBC 7-2-1997 standards. For fire-rated double door openings, code requires the inactive leaf to be secured at the top and bottom. The UNIFB820 satisfies that requirement automatically without relying on occupant operation. Confirm with your Authority Having Jurisdiction that this configuration meets local fire code for your specific door label before specifying.