Trimco 3911 Adjustable Dust Proof Strike

About this item

The Trimco 3911 is the adjustable dust proof strike from Trimco's flush bolt hardware line. It's the floor-mounted receptacle that receives the bottom flush bolt on a double door or active/inactive paired door set, designed specifically for installations where carpet or a threshold plate changes the floor height and requires a depth-adjustable strike rather than a fixed one.

What a Dust Proof Strike Actually Is

A dust proof strike is the spring-loaded floor fitting that accepts the bottom flush bolt when a door closes. Without it, the flush bolt would drop into a plain hole drilled in the floor, which collects dirt, grit, and debris over time and eventually prevents the bolt from seating cleanly. A dust proof strike keeps that pocket covered and clean. When the flush bolt descends, it depresses the spring-loaded cover and seats into the strike. When the bolt retracts, the spring closes the cover, keeping the socket clean for the next closure cycle. That's the function. The "dust proof" name describes the spring cover mechanism that protects the pocket, not a specific material or finish.

Why the 3911 Is the Adjustable Version

The Trimco 3910 is the standard dust proof strike with a fixed depth. The 3911 is the adjustable version. It uses a threaded spring carrier with a locknut that allows the depth of the strike pocket to be raised or lowered after installation by using the adjustment wrench that ships with every 3911. This adjustability matters in two specific installation situations. First, on carpeted floors, where the carpet pile reduces the effective floor height, the bolt needs a shallower strike depth to seat correctly. Second, on openings with a threshold plate, the threshold raises the floor surface and changes the bolt engagement depth. The 3911 handles both conditions without requiring a different part or a do-over on the floor prep.

The 3910 is the correct specification for hard floor installations at standard depth where no future adjustment is needed. If there's any chance the application involves carpet, a threshold, or future flooring changes, specify the 3911.

Compatibility with Trimco Flush Bolts

The 3911 is designed specifically for use with the Trimco 3800 Series Automatic and Semi-Automatic Flush Bolts. It's also recommended for Trimco Manual Flush Bolt assemblies. The 3910 and 3911 share the same design family. If your door schedule already specifies Trimco 3800 Series flush bolts on the inactive leaf of a pair of doors, the 3911 is the matching floor strike that completes that hardware assembly.

Large Target Area and ADA Compliance

The 3911 has a 3/4" diameter target area, which is larger than standard dust proof strikes. This larger target allows the flush bolt to seat reliably even when a door swings with slight misalignment. The spring mechanism uses a soft spring, which reduces the force required for the bottom bolt to engage and retract from the strike. The soft spring specification is specifically intended to aid ADA compliance on openings where hardware resistance must meet accessibility force thresholds.

Physical Specifications

Overall dimensions: 3/32" x 1-5/16" x 1-5/8". Face plate: 1-3/8" x 2-7/8" (removable). Projection: 1-1/2". BHMA designation L04021. Includes adjustment wrench. Made in the U.S.A. Available in brass, bronze, plated, and stainless steel finishes including 626 Satin Chrome and 630 Satin Stainless Steel.