Design Hardware UL Auto Flush Bolt (Metal Doors)

The UL-AFB-M ships with a rod sized for 7 foot doors. A 24 inch extension rod is available to take it up to 8 foot doors, but installing that extension rod voids the UL listing. If the opening is fire rated and has to stay listed, an 8 foot leaf is not the place for this bolt.

Plan the edge cutout around a 1 inch by 6-3/4 inch face plate, with a separate 1 inch by 2 inch guide mortised further along the edge for the rod. Bolt head is 1-1/2 inches and adjustable.

The Design Hardware UL Auto Flush Bolt is built for metal doors. For a pair of wood doors, the Ives FB41 is an automatic flush bolt set for wood doors with a 3/4 inch throw, matching the 3/4 inch bolt throw of the Design Hardware unit, and it carries a 90 minute fire rating. If you only need the top bolt on the inactive wood leaf, the Ives FB42 is a top automatic flush bolt for wood doors with an auxiliary fire latch.

The Design Hardware UL Auto Flush Bolt retracts automatically when the active leaf closes, so the inactive leaf can be pushed open without a separate step. If you want the inactive leaf held until staff deliberately release it, a manual flush bolt is the substitute: the ABH 1855S is a manual flush bolt single for metal doors with a 3/4 inch throw, the same throw as the Design Hardware bolt, and the ABH 1854 is a manual flush bolt set for metal doors supplied with a fire bolt. The Ives FB457 is a manual flush bolt for metal doors with a 12 inch rod.

The Design Hardware UL Auto Flush Bolt for metal doors is UL listed, but note that fitting the 24 inch extension rod for 8 foot doors voids that listing. Where the drawing calls for a 3-hour rating specifically, the ABH 1860P/1862P automatic flush bolt pair is fire rated 3-hour and uses a thermal lock mechanism.

Two things to budget for. At the floor, a DPS-1 dust proof strike keeps dirt out of the bottom strike so the bolt can seat; without it the pocket fills and the inactive leaf stops locking down. And if the leaves run to 8 feet, you need the 24 inch extension rod, which voids the UL listing.

An automatic bolt like the UL-AFB-M retracts on its own when the active leaf closes against the inactive one, so nobody has to walk over and throw a lever. Manual bolts have to be operated by hand at the top and bottom each time, which is fine on a leaf that stays shut but a problem where staff need both leaves open regularly. Manual options include the ABH 1854 set with fire bolt for metal doors and the Ives FB457 with a 12 inch rod for metal doors.

The UL-AFB-M is automatic only, with no cylinder provision. For cylinder control over the inactive leaf, look at the Adams Rite 1870 Series cylinder-operated flushbolt with key control, or the 1877 if the pair is wood.

An auto flush bolt secures the inactive leaf at both the head and the sill, so the rod run reaches from the mortised face plate through the guide to the bolt head. The supplied rod covers a 7 foot leaf; anything taller needs the 24 inch extension.

Usually debris in the floor pocket. A 3/4 inch throw bolt cannot seat if grit has filled the strike, which is why a DPS-1 dust proof strike is specified with this bolt; the spring-loaded cover keeps the pocket clear. The 1-1/2 inch adjustable bolt head also lets you dial the bolt down if the undercut at the sill is larger than planned.

The Design Hardware UL Auto Flush Bolt operates off the closing of the active leaf and has no cylinder. If the inactive leaf needs key control, Adams Rite offers cylinder-operated flushbolts: the 1870 Series is a cylinder-operated flushbolt with key control, and the 1877 is a cylinder-operated flushbolt for paired wood doors. For a keyed two-point setup, the Adams Rite MS1880/MS1881 two-point flushbolts use an interlock mechanism.

The Design Hardware UL Auto Flush Bolt is an automatic bolt for metal doors with a 3/4 inch throw and a 1 inch by 6 3/4 inch face plate, supplied with a rod for 7 foot doors. For a bottom-only replacement, the ABH 1858 is a universal bottom fire bolt with manual operation. If the existing bolts are manual singles, the ABH 1855S is a manual flush bolt single for metal doors with a 3/4 inch throw.

They solve different problems. The Design Hardware UL Auto Flush Bolt is an automatic bolt for metal doors with a 1 inch by 6 3/4 inch face plate, a 3/4 inch bolt throw, and a supplied rod reaching 7 foot doors. The Trimco 3999 is a 6 inch corner-mount flushbolt with a rounded end and the 3999SE is the square-end version of the same 6 inch corner mount; the Orca 86SQ is a 6 inch flush bolt with radius corners. Corner-mount bolts mount at the door edge corner rather than running a rod up the stile, and they are manually thrown, so the inactive leaf is not released by the active leaf closing.

The Design Hardware UL Auto Flush Bolt carries a 3/4 inch bolt throw with a 1 1/2 inch adjustable bolt head and a 1 inch by 6 3/4 inch face plate. The International Door Closers FB-1202 is a manual flush bolt with a positive U joint actuator, a 5/8 inch throw, a 1/8 inch offset with 7/8 inch backset, square end, and a guide included. The shorter throw and the fixed offset mean the FB-1202 needs strike prep that matches its own dimensions rather than reusing prep cut for the 3/4 inch Design Hardware bolt.

The Design Hardware UL Auto Flush Bolt is supplied as a bolt with a rod for 7 foot doors, installed top and bottom as separate bolts, and it includes a 15/16 inch by 2 1/4 inch strike and a 1 inch by 2 inch guide. If you want the top and bottom handled by a single two-point mechanism with automatic release, the Adams Rite MS2180 Series is an auto-release two-point flushbolt using the Smartlock mechanism.

Both the ABH 1855S manual flush bolt single for metal doors and the Ives FB358 manual flush bolt carry a 3/4 inch throw, the same throw as the Design Hardware UL Auto Flush Bolt; the FB358 uses a 1/2 inch bolt diameter and is fire rated. Throw matching means the existing strike depth still works, but face plate and guide cutouts differ by product, so confirm the plate dimensions against the 1 inch by 6 3/4 inch face plate and 1 inch by 2 inch guide the Design Hardware bolt uses before reusing the prep.

Three: 613 dark bronze, 626 satin chrome, and 606 satin brass. 626 is the usual match for commercial lever and exit hardware, 613 for dark bronze storefront and aluminum openings.

Where the opening is not rated and the doors are wood, a mortise-in flush bolt is the plainer option: the Delaney 4101 is a 7 inch slide type mortise-in flush bolt, the Delaney 4363 is a 7 inch mortise extension flush bolt, and the Delaney 4108 is a 6 inch square end solid brass flush bolt. The Design Hardware UL Auto Flush Bolt is the choice when the pair is metal and you want the inactive leaf to release automatically as the active leaf closes.

The Design Hardware UL Auto Flush Bolt is offered in 613 dark bronze, 626 satin chrome, and 606 satin brass, which suits commercial metal openings. For residential or decorative pairs where the flush bolt has to match a wider trim palette, Emtek flush bolts and the Delaney 4108 6 inch square end solid brass flush bolt are the lines to look at, keeping in mind those are manual bolts for wood doors rather than automatic bolts for metal.