Double Cylinder vs. Thumbturn Cylinder

When choosing a lock cylinder for a multipoint door lock, two common options are a double cylinder and a thumbturn cylinder. Both types work with the same multipoint locking system, but they differ in how the door is unlocked from the inside.

Understanding the difference helps avoid ordering the wrong part and ensures the door is safe and easy to use.

Click to enlarge: single vs double vs dummy cylinders

What a Lock Cylinder Does

The lock cylinder is the part of the door where the key is inserted. In a multipoint lock, turning the key does not just lock one spot; it activates the internal mechanism that locks the door at multiple points along the frame.

The cylinder type does not change how strong the lock is. It only changes how the door can be locked and unlocked from the inside.

Single Cylinder (Also Called Thumbturn Cylinder)

A single cylinder is often referred to as a thumbturn cylinder. These two names describe the same type of cylinder.

• Keyed on the outside
• Thumbturn on the inside
• Most common choice for residential doors
• Allows easy exit without a key

This type is popular because it allows the door to be unlocked quickly from the inside, which is important for everyday use and safety.

Double Cylinder

A double cylinder requires a key on both sides of the door.

• Keyed on both the inside and outside
• No thumbturn
• Prevents unlocking without a key
• Often used for added access control

Because a key is required to unlock the door from the inside, double cylinders are sometimes restricted by local fire or building codes on residential doors.

Dummy Cylinder (Non-Locking)

A dummy cylinder looks similar to other cylinders but does not use a key at all.

• No key operation
• Thumbturn only
• Common on interior or decorative doors
• Does not provide security locking

Dummy cylinders are not typically used on exterior multipoint locking doors.

Which Option Is Right?

Most residential multipoint doors use a single (thumbturn) cylinder because it balances security with easy exit. A double cylinder may be chosen when interior access needs to be controlled, but local codes should always be checked first.

All cylinder types work with the same multipoint locking mechanism, but the difference is how the door is operated from the inside.

Check out our article on cylinder projection for more information on installation.