Residential Deadbolts: Bolt Throw, Grade, Cylinder, Frame

What makes a deadbolt actually work

A deadbolt is a steel bolt that extends into the frame. It functions effectively only when three conditions are met: the bolt throws far enough into the strike, the cylinder resists manipulation long enough to deter casual attacks, and the frame can absorb the load applied to it.

The most common security mistake is to invest in an expensive deadbolt while leaving a thin strike plate with short screws in place^[1]. The correct approach pairs the deadbolt with a reinforced strike.

The grade system explained

ANSI/BHMA grades deadbolts on three tests: operational cycles for durability, strike resistance, and finish durability. The grading does not assess pick resistance, bump resistance, or bolt throw distance^[2].

Grade	Typical application	Adequate for home?
Grade 1	Commercial, high-traffic	Yes — overbuilt, never the wrong choice
Grade 2	Heavy residential	Yes — the correct default for most homes
Grade 3	Light residential	Marginal — only acceptable when paired with a reinforced frame

What actually determines forced-entry resistance

The grade indicates that the lock is well-made. Four additional specifications determine whether it will hold under attack:

1. Bolt throw of 25 mm (1 inch) minimum. A shorter throw can be levered out of the strike pocket during a pry attack.
2. Hardened steel bolt with anti-saw pin. A small hardened pin inside the bolt body spins when a hacksaw contacts it, preventing the bolt from being cut.
3. Anti-pick or anti-bump cylinder. Schlage SecureKey and Medeco's sidebar both address this. A standard Grade 2 cylinder is adequate for most homes, since lock picking requires skill and time that opportunistic intruders rarely bring.
4. Solid brass or cast zinc body, rather than thin stamped steel. This determines whether the cylinder housing deforms under a drill attack.

Cylinder classes

For most homeowners, a standard Schlage B60N or equivalent Grade 2 deadbolt is the right choice. For targeted attacks where key control and drill or pick resistance matter, a high-security cylinder such as Medeco Maxum or Mul-T-Lock Hercular is more appropriate.

Double-cylinder deadbolts that require a key on both sides are not a default recommendation. They reduce the risk associated with glass near the thumbturn but can block emergency egress if the key is missing. Most Canadian building codes prohibit them on designated egress exits.

Ranked product picks

What this guide does not address on its own

A strong deadbolt seated in a thin strike plate remains a weak system overall. Before relying on the deadbolt, review the strike plate guide first. For homes with glass beside the door or with a prior break-in history, also review the full door reinforcement guide.