Sash Window Security Restrictors

The burglar got past the lock.
He didn't get past these.

A customer's window after an attempted break-in. The lock tore out. The window stayed shut.

These photos come from a customer's home. Someone forced the lower sash so hard that the fitch lock tore clean out of the timber, screws and all. You can see the splintered wood where it let go.

The window still didn't open. A pair of security restrictors higher up the frame stopped it dead, and the intruder gave up.

Why restrictors hold when locks don't

A surface lock is only as strong as the two screws holding it to the sash. Restrictors are different. The body of each restrictor sits in a mortise cut into the timber, embedded in the frame itself, so there is no housing to lever off and nothing to tear free. Only a slim 86mm faceplate shows. The sash physically cannot travel past them.

Embedded in the frame, not screwed to the face.

Tested, not just claimed

• A traditional timber sash window fitted with these devices passed PAS 24:2016 enhanced security testing, including manipulation and mechanical loading tests (Wintech report R17136)
• Safety device load capacity of 350N verified to BS EN 14351-1:2006 by a UKAS accredited laboratory
• Tested to ASTM F2090, the window fall prevention standard, across four versions (2008 to 2017)

Read the PAS 24 security test report · Read the load test report

Set the window to open 150mm. No further.

The same fitting solves a second problem: children and open windows. Set the restrictors so the sash opens 150mm, or whatever height suits the room, and it stops there. Fresh air gets in and nobody climbs out.

When you want the window fully open for cleaning or a warm day, press the release and the sash slides right up. The restrictor resets itself automatically the next time you close the window. No key to find, nothing to remember.

You won't notice them. Neither will anyone else.

There's a pair fitted in this window, circled. Most visitors would never spot them.

Restrictors sit low and flush, and the finishes match the rest of your window hardware: polished brass, antique brass, polished chrome, satin chrome or white.

Fitting: a mortise, four screws, twenty minutes

1. Mark. Close and lock the bottom sash. Measure up from the top of the bottom sash to your chosen opening height and mark the frame.
2. Cut the mortise. A 57.5mm x 12.5mm slot, 15mm deep, with a drill and chisel or a router. This is what embeds the body in the timber.
3. Screw the faceplate down with the screws supplied, one device each side of the window.
4. Fit the buffer pad under each device and close the sash. The restrictors engage on their own.
5. Test it. Raise the sash to the stop, then press the release and check it opens fully.

Download the full fitting instructions (PDF) · Safety and operation guide (PDF)

Remember each window needs a pair. Order two per window you want secured.

Restrictors protect against accidental falls by young children but are not a substitute for supervision. Keep them engaged unless the window is needed for emergency escape, and never padlock them.