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What is a sash jammer, and should you fit one?
A sash jammer is a small extra lock screwed to the frame of a door or window, with a lever that swings over the opening part to stop it being forced. It adds a second point of security, but it does not replace the main lock and needs care on an escape window.
Last reviewed:What is a sash jammer?
A sash jammer is a compact extra lock. The body screws to the fixed frame of a door or window, and a lever or cam swings across the edge of the opening part, called the sash. With the lever across, the sash cannot be pushed or prised away from the frame. With it swung back, the door or window opens as normal.
Some sash jammers are plain and turn by hand. Others lock with a small key, so the lever cannot be moved from the outside or by a child. Most are sold in white, brown or chrome to suit common frame colours.
Where are sash jammers usually fitted?
They are most often seen on hinged doors and windows, both uPVC and timber:
- back doors and side doors, as a second point of security
- French doors and outward-opening windows on the ground floor
- windows in rooms that are not used much, where a second lock gives peace of mind
- doors where the main lock is old and you are waiting to have it replaced
They are not usually the right choice for sliding patio doors or vertical sliding sash windows, which work differently and have their own types of extra lock. Ask a locksmith which kind suits your frame.
Does a sash jammer replace the main lock?
No. The main lock and handle still do most of the work, and a jammer only holds the sash at one point. If your door lock is worn, the handle is loose or the frame is damaged, fixing that comes first. A jammer is an extra layer on a door or window that already closes and locks properly.
Insurance is a separate question. Policies set their own wording on locks. This page cannot say what your insurer requires, so read the policy or ask the insurer before you rely on any lock to meet a condition.
What about windows you might need to escape through?
This is the point to think about before you fit anything. Building guidance in England expects some windows to be usable as a way out in a fire. Approved Document B, Volume 1, paragraph 2.10 says locks, with or without removable keys, and opening stays with child-resistant release catches may be fitted to escape windows [S1].
So a keyed jammer on a bedroom window is not ruled out by that guidance, but a lost key is a real problem at night. If you fit one to a window you might need to climb out of, keep the key near the window, out of reach from outside, and make sure everyone in the house knows where it is. If you are unsure which of your windows matter for escape, ask the installer or the council's building control team.
Who should fit a sash jammer?
Fitting one is a small job, but it involves screwing into the frame. On uPVC, the screws have to go into the right part of the profile, away from the glass unit and the drainage channels, and the lever has to line up with the sash. Read the maker's instructions for your frame type before you start.
If you would rather have it done, a locksmith, a window installer or a handyman can usually fit one, often as part of a wider look at the door or window locks. Citizens Advice suggests getting written quotes from at least three traders [S2]. Ask each one to say whether the price includes the jammers themselves, and how many they will fit.
Jobs you might post
These are examples, not taken from real job posts. "Fit two keyed sash jammers to our uPVC back door and the kitchen window." Or: "Our French doors feel loose when locked. Please check the locks and fit extra security if needed." Or: "We have just moved into a house in Sandbach and want a locksmith to look at all the ground floor doors and windows."
Get quotes from local locksmiths
Post the job with photos of the doors or windows and your postcode. Up to five matched local businesses can reply [QZ2]. QuoteZila is free for customers and local businesses [QZ1]. QuoteZila is starting in Cheshire, and anyone in the UK can post or register.
Honest status: QuoteZila is new. We're starting in Cheshire, beginning with Crewe, Nantwich and Sandbach, and growing area by area. Anyone in the UK can still post a job or register a business. How fast you get quotes depends on how many local businesses have joined near you. Businesses can register and receive jobs straight away. We don't check insurance, qualifications or registrations, so please check these yourself before you hire.
Posting a job is not open yet
See the locksmiths page, the glaziers page or the locksmith cost guide. For handle problems, see uPVC window handle replacement.
Questions about sash jammers
What does a sash jammer do?
It holds the opening part of a door or window, the sash, against the frame. A lever or cam on the jammer swings across the edge of the sash so it cannot be pushed or pulled open, even if the main handle is forced. Some versions lock with a key and some simply turn by hand.
Can I fit a sash jammer on a uPVC door?
Sash jammers are commonly fitted to uPVC and timber doors and windows that open outwards or inwards on hinges. What matters is the frame profile and where the screws will go. Read the maker's instructions for your frame, or ask a locksmith or window installer to look at it.
Can a sash jammer go on an escape window?
Approved Document B, Volume 1, paragraph 2.10 says locks, with or without removable keys, and opening stays with child-resistant release catches may be fitted to escape windows. If you fit a keyed jammer to a window you might need to escape through, keep the key close by and make sure everyone in the house knows where it is.
Will a sash jammer satisfy my home insurer?
This page cannot say, because policies differ. Read your policy wording on locks, and ask the insurer if you are unsure. A jammer is usually an addition to the main lock, not a replacement for it.
Does QuoteZila check the locksmiths who quote?
No. We don't check insurance, qualifications or registrations, so please check these yourself before you hire. You can report a quote or a business from your job page.
Related trades
Cost guides
Related pages
- Door Jammed? Why It Sticks and What to Do. Why a door jams or sticks: swollen timber, loose hinges, a raised floor, a failed latch or a uPVC lock. What to check, and when to call a joiner or locksmith.
- Fire Door Locks: What You Can Fit and Ask. Can you fit a lock to a fire door? Why the lock counts as part of the door, what flat residents must agree first, and why exit doors must open fast inside.
Sources
- QZ1: QuoteZila product fact. QuoteZila home and jobs-for-tradesmen copy.
- QZ2: QuoteZila product fact. QuoteZila terms and matching notes.
- S1: Approved Document B (fire safety) volume 1: Dwellings, 2019 edition incorporating later amendments, paragraph 2.10, GOV.UK (Ministry of Housing, Communities and Local Government). Accessed 2026-10-25. https://assets.publishing.service.gov.uk/media/6aa3bb335f6e942efe37f150/AD_B1_2026.pdf
- S2: Before you get work done on your home, Citizens Advice. Accessed 2026-10-25. https://www.citizensadvice.org.uk/consumer/getting-home-improvements-done/before-you-get-building-work-done/