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A deadbolt lock cannot be moved to the open position from the outside except by rotating the lock cylinder with the key.

A deadbolt can be either single cylinder or double cylinder. A single cylinder deadlock has a key cylinder on one side of the lock, but is operated by a thumbturn on the other side. Double cylinder locks have a key cylinder on both sides. This prevents unwanted unlocking of the door by forced access to the interior thumbturn (via a nearby window, for example). Double cylinder locks are not recommended for residential applications because they violate fire safety regulations.

American National Standards Institute (ANSI) has designated voluntary performance standards for builder's hardware. The various grades set requirements for the minimum acceptable requirements for Operation (key torque; cycles) and Security (pull strength, impact resistance).

Grade 1 certification – Highest Grade Security
Grade 1 is the strongest grade ANSI/BHMA will supply for any Residential or Commercial product. This lock has been tested to 250,000 open/close cycles, has a bolt that projects 1 inch (2.54 cm) into the door frame, and can withstand 10 hammer blows without giving way.

Grade 2 certification – Higher Residential Security
Grade 2 is designed and built to offer excellent security and durability for more residential applications and some light commercial applications. This lock has been tested to 150,000 open/close cycles, also has a bolt that projects 1 inch (2.54 cm) into the door frame, and can withstand 5 hammer blows without giving way.

Grade 3 certification – Basic residential security
Grade 3 is the lowest grade provided by ANSI, the minimal acceptable quality for residential door locks. This lock has been tested to 100,000 open/close cycles, also has a bolt that projects 1 inch (2.54 cm) into the door frame, but is only required to withstand 2 hammer blows without giving way.

Proper Installation
The strike plate is a metal plate attached to the door jamb which receives the bolt. For maximum security, the plate should be installed using 3-inch (7.62 cm) screws. By using long screws, the strike is secured to the door frame stud, not just the jamb. In addition, deadbolts should also have a reinforced strike plate with off-set screw holes. This will ensure that the screws aren't driven into the same grain of wood. If someone tries to kick in the door, the jamb will normally give way before the deadbolt, but the extra long screws and reinforced plate will stand up to some serious pounding.