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How to fit a window restrictor

Updated: 16 October 2026

You have a packet of screws and either a uPVC casement or a timber sash. The job is to put the plates where the cable, or the Yale staple, meets sound material and stops short of glass or steel. This is how to fit a window restrictor without treating another brand's sheet as your box contents. Which type to buy is on the [window lock buying guide](/hub/burglar-protection/window-lock/sub/window-lock-buying-guide), and prices are on the [window lock comparison](/hub/burglar-protection/window-lock). If you buy through our links, we may earn a commission at no extra cost to you. The page is from the Products Compared editorial team. These steps were not a lab fit.

You have a packet of screws and either a uPVC casement or a timber sash. The job is to put the plates where the cable, or the Yale staple, meets sound material and stops short of glass or steel.

Our top picks

Schlosser Technik Schlosser Technik cable restrictor, 2 pack

Best overall

Schlosser Technik Schlosser Technik cable restrictor, 2 pack
8.6/10about £13.40
View offer
XFORT XFORT Viper cable restrictor, 4 pack

Preis-Tipp

XFORT XFORT Viper cable restrictor, 4 pack
8.3/10about £18.99
View offer
Yale Yale 8K101 window latch, 4 pack

Alternative

Yale Yale 8K101 window latch, 4 pack
8.4/10about £20.98
View offer
On this page
  1. 1.Check the frame before you drill
  2. 2.Fit a keyed cable restrictor
  3. 3.Wide sashes, adhesive, and the timber latch
  4. 4.When to stop

Check the frame before you drill

uPVC is hollow, often with steel inside, and the glass is closer than a long screw expects. If a screw spins, take it out. Timber only works when it is sound. Stay clear of the keeps, the friction stay and the handle. A TSS sheet for a different cable specifies 4.2 x 45 mm screws. Do not assume these packs contain them. Several XFORT reviewers found the supplied screws too long for uPVC and used 4 x 25 mm. If you rent, wait for the landlord.

Fit a keyed cable restrictor

Put the body on the fixed frame and the cable end on the sash, clear of the handle. Hold the sash at the opening you want, let the cable sit taut, and mark both plates. Marking with the sash shut does not set the gap. On a wide casement the gap beside the cable is not the gap at the far end. A pilot stops the screw skating on plastic. Other brands mention 2.0 mm or 3 mm. One stored Schlosser review used 2.5 mm and described about 100 mm with the cable stretched. Do not copy those figures as a specification the pack does not print. Drive until the plate is firm, then stop before the plastic creaks. Lock the cable, remove the key, and try the sash. If this window is an escape route, the key stays where an adult can reach it at night. Which millimetre rule applies is on window restrictor child safety.
Schlosser Technik Schlosser Technik cable restrictor, 2 pack

Testsieger

Schlosser Technik Schlosser Technik cable restrictor, 2 pack
8.6/10about £13.40
View offer

Wide sashes, adhesive, and the timber latch

Measure a wide sash along the whole opening with the cable taut. The sash swings, so one restrictor by the handle can leave the far corner wider. A second restrictor closes that gap. Adhesive is printed on several multipacks. Stored reviews on the shared pool say a pad was pulled off, including by a strong child, and screws held. Above the ground floor, screw it. The unbranded four-pack with a 7.5 × 3.2 cm face has no reviews. The Yale 8K101 is a surface latch for an outward-opening hinged timber casement, not a cable and not uPVC. Staple on the frame, body on the sash, marked with the window shut. Do not copy 50 mm from another shop.

When to stop

Stop if the timber is rotten, a screw spins, or the bit is about to meet steel or glass. Stop if you cannot say how an adult opens this window at night, if someone has named PAS 24, or if you are a tenant without consent. A joiner, a locksmith or the landlord takes those cases. The fit is done when the widest gap is the one you marked and the plates do not move. If the far corner is still wider, add a second restrictor or take the first one off.

Common questions

Where do the cable and the lock body go?
Put the body on the fixed frame and the cable end on the opening sash, clear of the handle, so the cable runs straight at the opening you want. Mark with the sash held at that opening. Test again with the key removed, and check you can still release it when the key is back.
Do I need a pilot hole in uPVC?
A small pilot stops the screw skating. Other sheets mention 2.0 mm or 3 mm, and one stored Schlosser review used 2.5 mm. None of those is the rule for every pack here. Stay clear of steel and glass, and do not keep driving a screw that spins.
What if the supplied screws feel too long?
Stop before the screw meets reinforcement or the glazing. Several XFORT reviews found the supplied screws too long for uPVC and used 4 x 25 mm. That is an observation, not the contents of every box. A TSS sheet's 45 mm screws belong to that sheet.
Can I rely on the adhesive pads?
Only on a clean, dry, flat face, and not as the only fixing where a fall would injure someone. Stored reviews say pads were pulled off and screws held. A wipe in the box does not change that. If you cannot drill, ask the landlord.
Is one restrictor enough on a wide window?
Often it is not. The gap beside the cable can be right while the far end is wider, because the sash swings. Measure the whole opening with the cable taut, and add a second restrictor if that far gap is larger than you intended.
How do I fit a Yale 8K101?
Close the timber sash, fix the staple to the frame and the body to the opening section, and turn the key so it clenches shut. The listing includes screws and one key for four locks. It is not for uPVC and it is not a ventilator. Lengths quoted on other shops are not this comparison's specification.
When should I stop and call someone?
Stop for rot, a spinning screw, or a bit about to hit steel or glass. Stop if the night-time release is unclear, if PAS 24 or a named lock was specified, or if the window is listed or commercial. Tenants need consent before holes. A joiner, a locksmith or the landlord should take those cases.

Related pages

Cable restrictor vs window latch

Window locks

Best window lock: which listing matches your frame

Window lock buying guide: job, frame, fixing and key

Window restrictor child safety: gap, key and rules

Sources

Public UK sources and the amazon.co.uk listings in this comparison. Listings captured 15 October 2026. Page updated 16 October 2026.

  1. Approved Document K (2013) (retrieved 15 October 2026)
  2. Approved Document Q (retrieved 15 October 2026)
  3. HSE: falls from windows (retrieved 15 October 2026)
  4. CWCT: are window restrictors designed to resist adequate loads (retrieved 15 October 2026)
  5. BSI: PAS 24:2022+A1:2024 (retrieved 15 October 2026)
  6. AXA Connect LC01 locks requirement (retrieved 15 October 2026)
  7. MLA minimum security requirements, January 2025 (retrieved 15 October 2026)
  8. RoSPA: falls (retrieved 15 October 2026)