Mul-T-Lock HDC-05 Hercular Double Cylinder Captive Key Deadbolt Brass 006 Keyway

Captive Key Deadbolt Design

The Mul-T-Lock HDC-05 Hercular uses a captive key mechanism that combines single and double cylinder operation. A special thumb-turn key locks into the inner cylinder for single-cylinder convenience and emergency egress. Removing that key and using a standard key in the second inner cylinder converts the lock to double-cylinder security. This hybrid function suits residential or commercial doors where both safety and controlled access are required.

Adjustable Backset Installation

The deadbolt fits doors with a backset adjustable between 2-3/8 inches and 2-3/4 inches, covering common door preparations. It mounts in a standard cylindrical bore without specialised tooling. The UL fire-rated latch satisfies building-code requirements for fire doors. Two keys and a key ID card are supplied in the box, supporting Mul-T-Lock's key control system for restricted duplication.

High-Security Cylinder Rating

The lock cylinder meets ANSI Grade 1 standards and UL 437 certification for drill and pick resistance. Bump-proof construction protects against common forced-entry techniques. Bright brass finish provides corrosion resistance for interior or exterior use. The double-cylinder mode removes the thumb-turn entirely, eliminating inside manipulation through glass or letter slots. Buyers needing electronic access, smart-home integration or a higher key-count than two must specify a different product.