Technical Foundation
What Is a Deadbolt Lock?
Deadbolts are rated under ANSI/BHMA A156.36 into Grade 1, 2, or 3, based on standardized tests for cycle life, and resistance to force attacks like kicking and prying — Grade 1 is the highest-security commercial-duty rating, Grade 2 is residential/light-commercial, and Grade 3 is the minimum consumer-grade standard. This grade, not brand reputation alone, is the objective spec that determines the lock's actual resistance to forced entry.
Single cylinder deadbolts use a key on the exterior and a thumb-turn on the interior, while double cylinder deadbolts require a key on both sides — often specified where a nearby window could let an intruder reach through and turn an interior thumb-turn, but some fire codes restrict double cylinder locks on exit doors due to the risk of trapping occupants during an emergency evacuation. Backset (the distance from the door edge to the bolt's center) must match the door prep exactly.
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| Spec | What It Means | Why It Matters |
|---|---|---|
| ANSI/BHMA Grade | Grade 1 (commercial), Grade 2, Grade 3 | Grade 1 offers the highest tested resistance to forced entry and highest cycle life |
| Cylinder Type | Single cylinder (thumb-turn inside) vs. double cylinder (key both sides) | Double cylinder adds security near windows but may violate fire/exit code on egress doors |
| Backset | Commonly 2-3/8 in. or 2-3/4 in. | Must match the existing door prep hole spacing exactly, or the door needs re-boring |
| Bolt Throw | Length the bolt projects into the frame, typically 1 in. for Grade 1 | Longer bolt throw increases resistance to prying and impact forcing |
| Strike Plate | Standard vs. reinforced/security strike plate | A reinforced strike plate anchored into the door frame stud significantly increases kick-in resistance |
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Applications
Where Deadbolt Locks Get Used
Deadbolts are specified anywhere a door needs bolt-style security independent of the primary latch, graded to the security level the application requires.
Residential Exterior Doors
Grade 2 single cylinder deadbolts as standard home security on front and back entry doors.
Commercial Office & Retail Entry
Grade 1 deadbolts meeting commercial building code and insurance requirements for entry security.
Multi-Family & Apartment Buildings
Durable, high-cycle-life deadbolts standing up to frequent daily use across many residents.
Storage & Warehouse Access Doors
Heavy-duty commercial deadbolts securing secondary and service entry points.
Short-Term Rental & Hospitality
Keyless keypad deadbolts allowing code-based access management without physical key handoff.
Government & Institutional Facilities
Grade 1 rated deadbolts specified to meet facility security and procurement standards.
FAQ
Deadbolt Locks Questions, Answered
What's the practical difference between Grade 1, 2 and 3 deadbolts?
The grades come from standardized ANSI/BHMA testing for cycle life and resistance to force attacks like kicking and hammering. Grade 1 is commercial-duty and offers the highest tested security and durability; Grade 2 is a step down, common in better residential products; Grade 3 is the minimum standard and is what's typically found in basic consumer hardware. For higher-security needs, specify Grade 1 or 2 explicitly rather than assuming.
Should I install a single or double cylinder deadbolt?
A single cylinder deadbolt (key outside, thumb-turn inside) is standard and allows quick exit in an emergency. A double cylinder deadbolt (key required on both sides) is sometimes chosen where a nearby window would let an intruder reach in and turn a thumb-turn — but many fire and building codes restrict or prohibit double cylinder locks on required exit doors because they can trap occupants during a fire. Check local code before specifying double cylinder on an egress door.
How do I know what backset I need?
Backset is the distance from the edge of the door to the center of the bolt hole, most commonly 2-3/8 in. or 2-3/4 in. in North America. Measure your existing door prep or check the door manufacturer's spec — many deadbolts include an adjustable backset that covers both common sizes, avoiding the need to re-bore the door.
Does a reinforced strike plate really improve security?
Yes, significantly — a standard strike plate is often held by short screws into the door jamb trim alone, which can split under a kick. A reinforced strike plate uses longer screws anchored into the structural door frame stud, which substantially increases resistance to forced entry even with the same deadbolt grade.
Are keyless keypad deadbolts as secure as traditional key deadbolts?
A quality keyless deadbolt still uses the same graded bolt mechanism as a traditional deadbolt — the keypad simply replaces the key-and-cylinder entry method. Security is comparable if the underlying bolt mechanism carries the same ANSI grade; the keypad adds convenience for code-based access management rather than changing the core bolt security.
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