Article

Single vs Double Cylinder and Egress

Updated October 11, 2026

Double cylinder: keyed both sides

A double-cylinder deadbolt needs a key inside and out. It stops intruders from reaching through broken glass to turn the thumbturn. It also stops you from leaving fast in a fire without the key.

The egress rule

Most US residential codes require single-action egress from sleeping rooms: one motion, no key, no tool. Double cylinders on bedroom or required-egress doors violate this in many jurisdictions and can void insurance claims. Check the locally adopted code — not the internet — before installing.

Safer answers to the glass problem

• Single cylinder plus security film on nearby glass — keeps one-motion exit.
• Double cylinder only where legal — typically non-sleeping doors, and only with the key left in a known spot (which partly defeats the purpose).
• Keyed entry plus auxiliary lock used only when home.

Model the swap in the rekey checker and confirm handing and prep in the fit checker.