Strike Plates: Where the Bolt Meets the Frame

Latch Strikes vs. Deadbolt Strikes

A156.2 defines a latch bolt as a component "having a beveled end which projects from the lock front in its extended position, but is forced back into the lock case by end pressure." That beveled end is what lets a spring latch close by itself. As the door swings shut, the bevel meets the strike and is pressed back, then extends into the strike opening. A deadbolt has no bevel and is thrown only after the door is closed.

The strikes reflect those two jobs:

• Latch strikes usually have a lip, a projecting extension of the plate beside the opening. Manufacturers sell latch strikes in several lip lengths. Allegion lists Schlage L-Series mortise strike lips from 7/8" (flat) to 2", with 1-3/16" standard for 1-3/4" doors. Schlage's ND catalog offers its strikes "in a variety of lip lengths to accommodate different door preps."
• Deadbolt strikes can be flat. Schlage's B500 residential deadbolt ships with a square-corner strike with "no lip," furnished with a metal dust box as standard.

A dust box (also called a strike box) is the enclosed pocket behind the strike opening. Schlage describes the B500's metal dust box as providing "deep anchoring and added strength."

Deadlocking Latches Depend on the Strike

Many latches include an auxiliary deadlatch plunger beside the main latch. BHMA defines a deadlocking latch bolt as one "incorporating a plunger which, when depressed, automatically locks the projected latch bolt against return by end pressure." The plunger has to stay depressed against the strike for that locking to happen.

Manufacturer installation notes say this directly:

• A dormakaba installation bulletin for its E-Plex 7900 cylindrical lock says the deadlocking plunger must contact the strike plate when the door is closed and "must not enter the strike plate opening." It adds that "a gap greater than 1/8" between the latchbolt and strike plate may reduce security and/or cause improper latch operation."
• ERA's fitting instructions for its 3000 series digital lock carry the same warning: the plunger "must not enter the strike plate aperture."

That is why strike alignment matters for more than smooth closing. See door latches and loiding for why deadlocking exists.

Common Strike Sizes

Frames are prepared for particular strikes, so the strike has to match the frame. Two sizes appear in Schlage's own documents:

Other sizes and shapes exist, and exact preps vary by frame and product, so the manufacturer's template governs. BHMA publishes preparation standards so that hardware fits common door and frame preps. For example, ANSI/BHMA A156.115 "cover[s] all significant dimensional attributes for mounting common hardware products in steel doors and frames."

Reinforcement and the Frame

Some manufacturers tie the strike into the framing behind the jamb:

• Schlage's B500 specification describes a door frame reinforcer: a metal dust box reinforcer "concealed under the strike and... deeply anchored to the jamb with three 3" (76 mm) long screws." Schlage says it "significantly strengthens a wood jamb against 'kick-in' attack."
• Schlage's B600-series sheet lists an "exclusive concealed wood frame reinforcer" that "protects wood jamb against kick-in attacks," paired with a 1-inch-throw deadbolt.

Standards reflect the importance of that whole load path. BHMA's summary of the residential deadbolt standard, A156.40, says its security tests include "loading the door against the deadbolt with 1,350 pounds of force." See deadbolts for throw length and single- vs double-cylinder design, and ANSI/BHMA lock grades for how deadbolt testing differs from bored locksets.

A strong strike works as part of a system that also includes the door, frame, hinges, and lock.

Special Strikes

• Electric strikes replace the fixed strike with an electrified keeper that can release a latch for access control. See electric strikes.
• Exit device strikes receive the latches of panic hardware. Von Duprin's catalog lists device-specific strikes and mullions prepared for them, and notes that strikes "should be ordered with device."
• Strikes on fire doors must be part of a listed assembly. For electric strikes, an NIH technical bulletin states that "fail secure strikes must be used, per NFPA 80," and Allegion's I Dig Hardware notes that fail-safe electric strikes are not listed for fire doors. See fire-rated door hardware.
• Mortise lock strikes are made for mortise lock latches; see mortise locks.

Strikes and Everyday Operation

Because the strike, latch, and door closer work together, a door that closes and latches every time is also a door whose lock can do its job. Manufacturer instructions, like the dormakaba bulletin above, stress accurate alignment between the strike and latchbolt centers.

Related Topics

• Deadbolts: throw length, reinforcement, and grades
• Door latches: spring latches and deadlocking plungers
• Electric strikes: electrified strikes for access control
• Loiding: the latch bypass deadlocking is designed to stop
• Cylindrical locks: bored locksets and their latches
• Door closers: getting the door closed and latched

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