How To Choose The Right Door Bolt


Published: November 2020 | Last Reviewed: 17 September 2026

This post is part of our regularly reviewed content series, ensuring all advice remains accurate and relevant to your home project.

Author: Carl Benson

Carl is the founder of Suffolk Latch Company, with a background in engineering and over 20 years’ experience in home hardware. He works closely with suppliers and designers to develop quality ironmongery that stands the test of time. Read my full bio.

Carl Benson

Introduction

Choosing the right door bolt begins with understanding what you need it to do. A bolt used to provide privacy on a bathroom door has different requirements from one securing the inactive leaf of a pair of French doors or holding the lower section of a stable door closed.

You will also need to consider whether the adjoining surfaces are level, whether the bolt will be fitted vertically or horizontally and whether it is suitable for internal or external use.

This guide explains the differences between surface-mounted door bolts, flush bolts, rack bolts and morticed deadbolts. You can also browse our complete door bolt collection.

Door bolts fitted to a pair of timber doors

Table of Contents

  1. What Does the Door Bolt Need to Do?
  2. Straight and Cranked Surface Bolts
  3. Choosing the Correct Bolt Size
  4. Lever-Action Flush Bolts
  5. Rack Bolts
  6. Bathroom Deadbolts
  7. Bolts for External Doors and Gates
  8. Door Bolt Safety and Security
  9. FAQ

What Does the Door Bolt Need to Do?

Before choosing a design or finish, decide where the bolt will be fitted and what function it must perform.

  • Internal privacy: A surface bolt can provide simple privacy on a bedroom or traditional internal door.
  • Bathrooms and cloakrooms: A bathroom deadbolt with a compatible turn and release normally provides a more practical arrangement, including emergency access from outside.
  • Stable doors: A surface bolt can hold the upper or lower leaf independently when the two sections are closed together.
  • Double or French doors: Flush bolts can secure the inactive leaf at the top and bottom.
  • External doors and gates: The bolt must be specifically approved for exterior use and suitable for the degree of weather exposure.
  • Additional security: Concealed rack bolts may supplement an appropriate primary lock, but the complete door and locking arrangement must suit the property’s security requirements.

A door bolt should not automatically be treated as the primary security lock for an entrance door. Check the requirements of your home insurer and seek advice from a qualified locksmith when security is the main concern.

Straight and Cranked Surface Bolts

Surface-mounted bolts are fitted to the face of a door rather than concealed inside it. They are available in straight and cranked versions.

Straight Door Bolts

Choose a straight bolt when the face of the door and the receiving surface are level. The sliding bolt travels directly into a receiver bridge or mortice plate without needing to cross an offset.

Cranked Door Bolts

A cranked bolt—sometimes called a necked or swan-neck bolt—is designed for surfaces that are not level. Its shaped bolt projects across the offset and normally enters a receiver plate fitted into the adjoining surface.

Measure the difference between the two surfaces before ordering. The shape and projection vary between products, so consult the individual dimensions rather than assuming every cranked bolt will accommodate the same offset.

Comparison between straight and cranked door bolts

Browse our traditional hand-forged door bolts for straight and cranked designs in a range of styles and finishes.

Choosing the Correct Bolt Size

The quoted size generally describes the overall or nominal bolt length, but the exact measurement method varies between designs. Always check the technical drawing before ordering.

As a general guide:

  • Small bolts: Suitable for cupboards, cabinets and lighter internal doors.
  • Four-inch bolts: A common choice for standard internal doors and stable-style doors.
  • Six-inch bolts: Better suited to larger timber doors where a longer and more substantial fitting is appropriate.
  • Larger bolts: May be required for gates, barns and heavy doors, provided the design and finish are suitable for the application.

Size alone does not determine security or suitability. The door construction, fixing material, screw length, receiver position and strength of the surrounding timber are equally important.

Lever-Action Flush Bolts

Lever-action flush bolts provide a discreet way to secure the inactive leaf of a pair of double or French doors. The bolt body is recessed into the door edge or face so that the fitting remains comparatively unobtrusive when the doors are open.

Flush bolts are commonly fitted at the top and bottom of the inactive door. Operating the small lever projects the bolt into a receiver in the head of the frame, threshold or floor.

Accurate morticing and alignment are important. The receiver must be positioned so that the bolt engages freely without forcing the door out of alignment. If you are unsure, ask an experienced joiner to fit the bolts.

Lever-action flush bolt for double or French doors

Rack Bolts

Rack bolts are concealed security bolts morticed into the edge of a timber door. They are commonly fitted in pairs, with one positioned near the top and another near the bottom.

Depending on the design, a rack bolt is operated using a dedicated key or compatible thumbturn. The visible operating point is fitted to the face of the door while the bolt mechanism remains concealed within it.

Rack bolts can provide additional security, but they must be positioned carefully to avoid weakening narrow door stiles, damaging glazing or interfering with existing locks. Follow the manufacturer’s measurements and fitting instructions.

Concealed rack bolt with a coordinating thumbturn

Bathroom Deadbolts

A bathroom deadbolt is a compact morticed mechanism fitted into the edge of an internal door. It is operated by a separate bathroom turn and release.

The thumbturn on the inside projects the bolt into the strike plate, while the external release allows the door to be unlocked in an emergency. This makes it a more suitable privacy arrangement for many bathrooms and cloakrooms than a surface bolt positioned only on the inside.

A bathroom deadbolt does not operate the door handle or knob. When a door also needs to latch closed, the handle or knob normally operates a separate tubular latch.

Alternatively, a bathroom sash lock combines the latch and privacy bolt in a single morticed lock case. Compatibility depends on the selected door furniture, spindle sizes and fixing centres.

Browse our tubular latches and bathroom deadbolts.

Comparison between sash locks and tubular bathroom deadbolts

Bolts for External Doors and Gates

Only use a bolt outside when the product description confirms that its material and finish are suitable for exterior use. Standard black beeswax hand-forged bolts are generally intended for internal doors and protected areas.

Exterior bolts may use powder-coated cast iron or a specialist weather-resistant coating. Even then, they should be inspected regularly, particularly around moving parts, screw holes and other areas where friction can damage the surface.

Coastal locations require additional care because salt carried in the air accelerates corrosion. Check the individual product information, as some exterior finishes may still be unsuitable for exposed coastal settings.

Browse our outdoor bolts for designs intended for gates, sheds and suitable external doors.

Door Bolt Safety and Security

A correctly chosen bolt should suit the door’s purpose without creating an avoidable safety problem.

  • Avoid fitting an internal surface bolt where a young child could lock themselves inside without an emergency means of access.
  • Do not rely on a small privacy bolt as the primary security lock for an external entrance door.
  • Check that bolts fitted to escape routes do not conflict with fire-safety or building requirements.
  • Make sure the receiver is fixed into sound timber or another suitable structural surface.
  • Do not position morticed bolts where they could weaken a narrow door stile or interfere with glazing.
  • Check your insurer’s requirements before changing the primary locks on an external door.
  • Ask a qualified locksmith or experienced joiner for advice if security, fire safety or accessibility is uncertain.

Whichever design you choose, check the product dimensions and supplied components before drilling or cutting the door.

FAQ

What is the difference between a straight and cranked door bolt?

A straight bolt is used when the door and receiving surface are level. A cranked bolt has an offset shape and is intended for surfaces that sit at different levels.

What size bolt should I use on an internal door?

A four-inch bolt is commonly suitable for a standard internal timber door, while a six-inch bolt may better suit a larger or heavier door. Always check the product drawing, door construction and intended use.

Can a door bolt be fitted vertically?

Some spring-tensioned bolts can be fitted vertically or horizontally without the slider dropping. Check the individual product description, as not every bolt is designed for both orientations.

Can I use an internal door bolt on a garden gate?

No, unless the product is specifically approved for exterior use. Standard internal finishes can corrode quickly when exposed to rain, condensation and changing temperatures.

Is a bathroom deadbolt the same as a surface bolt?

No. A bathroom deadbolt is morticed into the door and operated by a turn and release. A surface bolt is fixed visibly to the face of the door and normally has no external emergency release.

Are door bolts secure enough for a front door?

A bolt may provide supplementary restraint, but it should not automatically be treated as the primary security lock. Use an appropriate locking system and check your insurer’s requirements.

What is a flush bolt used for?

Flush bolts are commonly used to secure the inactive leaf of double or French doors. They are recessed into the door and usually project into receivers at the top and bottom.

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