A casement fastener is a simple turn-operated catch for casement windows, shutters or hopper sashes, in which a rotating wire, hook or pin engages a keep on the frame to hold the window closed. It is one of the older types of window hardware and is still often found in historic buildings and listed monuments.
How does a casement fastener work?
The fastener consists of two parts:
- The rotating piece — a lever, wire or arm on the moving sash
- The keep — a hook, eye or recess on the jamb
By turning the lever a quarter- or half-turn, the rotating piece engages the keep and locks the window. To open or close, it slides past or around the keep.
Types of casement fasteners
Over time, several types have developed:
- Espagnolette — a long rod that locks the window top and bottom at the same time, operated by a lever
- Cremone fastener — a variant operated by a handle
- Olive knob (oval cock) — a small handle with an oval rotating piece
- Turn-buckle (twist catch) — a simple rotating tab, often used on shutters
- Hook and eye — a basic hook engaging a fixed eye
Applications
Casement fasteners are used on:
- Historic windows — especially in 17th–19th century buildings
- Monumental shutters — as shutter hardware
- Garden houses and small outbuildings
- Restoration projects — preserving original hardware
Properties
- Simple — few parts, easy to repair
- Not burglar-resistant — insufficient for modern security requirements
- Traditional look — fitting for older buildings
- Inexpensive to make — often still produced by hand
For burglary-sensitive locations, casement fasteners today are usually combined with a multi-point lock or additional security fittings.
Related terms
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