To provide a discreet yet powerful layer of home security, the 37mm Rack Bolt is the professional choice for reinforcing timber doors and windows. Engineered to be morticed entirely within the door leaf, this concealed hardware provides a robust mechanical locking point that is virtually invisible from the exterior, making it an essential component for residential security upgrades and “fit-and-forget” property protection.

In the world of domestic security, the 37mm Rack Bolt is favored for its ability to provide high-strength locking without compromising the architectural aesthetic of a door. Unlike surface-mounted bolts that can be unsightly, the rack bolt (often called a “mortice bolt”) is installed inside the door timber. It is operated via a specialized star-shaped key that passes through a small, decorative escutcheon on the interior face.

The “37mm” measurement refers to the compact case length, designed to fit into standard door stiles and window frames where space is limited. With a 17mm width, this bolt requires minimal timber removal, preserving the structural integrity of your doors while providing a formidable barrier against forced entry, “shimming,” or “kicking.”

Why the 37mm Rack Bolt is the Professional Choice

Discreet Concealed Design: When retracted, the bolt is completely hidden. This makes it the ideal choice for heritage properties, high-end renovations, and modern minimalist interiors.
Star-Key Security: The splined “star” drive requires a specific key to operate, preventing intruders from using standard screwdrivers or tools to manipulate the lock from the inside.
Durable Locking Mechanism: Constructed with a hardened steel bolt and a precision-cut rack-and-pinion gear, the 37mm Rack Bolt provides a smooth, reliable throw that resists physical tampering.
Universal 37mm x 17mm Case: This industry-standard sizing makes it the perfect “drop-in” replacement for existing worn-out bolts or a straightforward addition to new door sets.
Versatile Application: While primarily used at the top and bottom of external doors for “triple-point” security, it is also highly effective on casement windows and French doors.
Choice of Finishes: Available with a variety of faceplates and escutcheons—including Satin Chrome, Polished Brass, and Matte Black—to match your existing door furniture.

Technical Specifications of 37mm Rack Bolt

Feature	Specification
Case Length	37mm (Compact Mortice Profile).
Case Width	17mm (Standard Slimline).
Bolt Material	Hardened Steel (Zinc Plated).
Operation Type	Star Key / Spline Drive (Internal).
Backset	Typically 32mm (Distance to key center).
Standard Finishes	Satin Chrome, Polished Brass, White, Black.

Professional Installation for Maximum Protection

Because the 37mm Rack Bolt is a mortice-style fitting, the precision of the installation directly impacts its security rating.

Vertical & Horizontal Placement: For external doors, professionals recommend installing one 37mm Rack Bolt approximately 150mm from the top and one 150mm from the bottom. This prevents the door from being “peeled” away from the frame at the corners.
Pilot Hole Accuracy: Use a 17mm or 18mm spade bit to drill the main mortice hole. Ensure you drill perfectly straight; if the hole is angled, the key will not align with the internal star-drive.
The “Keyhole” Alignment: Mark the center of the keyhole on the door face with extreme care. Use a small pilot drill (approx. 2mm) from the inside to ensure you have hit the center of the bolt’s drive before enlarging the hole for the escutcheon.
Reinforced Strike Plates: Always use the provided strike plate on the door frame. Without it, the bolt could split the timber frame under pressure. Use 35mm stainless steel screws for the strike plate to ensure it bites into the structural wall studs.
Dry Lubrication: Every 12 months, apply a quick puff of dry graphite lubricant into the keyhole. Avoid using wet oils or WD-40, as these can attract dust inside the rack-and-pinion gears, leading to a “crunchy” or stuck operation.

A Small Investment for Total Peace of Mind

The 37mm Rack Bolt is one of the most cost-effective ways to significantly upgrade your home’s security. It provides an additional layer of protection that is both easy for the homeowner to use and exceptionally difficult for an intruder to bypass. By choosing a high-quality 37x17mm bolt with a durable locking mechanism, you are investing in long-term safety and architectural elegance.

This 37mm Rack Bolt provides an extra layer of security for doors, offering a concealed locking mechanism that is both strong and reliable. Commonly used on wooden and timber doors, it is an effective way to enhance protection in residential and commercial settings. The compact 37mm x 17mm size ensures a discreet fit while delivering dependable security without affecting the overall appearance of the door.

Manufactured from durable materials, this rack bolt is designed for long-lasting use and consistent performance. Its concealed design makes it resistant to tampering, providing added peace of mind for home and office security. Easy to install with fixings included, it is suitable for use on side doors, back doors, storerooms and other areas where additional protection is required, making it a practical and secure hardware solution.