Sash Window Locks vs Standard Window Latches: Which Actually Protects You?

October 31, 2026

Standard sash fasteners hold a window closed and provide almost no security, because the catch can be released by sliding a thin blade between the meeting rails and rotating it. A keyed sash lock or a sash stop bolts the two sashes together independently of the fastener and cannot be released from outside. For ground floor and accessible sash windows, the keyed version is the one that actually protects.



Sash windows are a defining feature of older homes across Bayside and they are usually fitted with the same fastener design that has been in use for more than a century. The fitch fastener, the familiar curved catch that rotates to draw the two sashes together, does its original job well. That job was holding the window shut and reducing rattle. Security was not part of the specification, and it is not part of the performance.

How the Standard Fastener Is Defeated

The two sashes in a double hung window meet at the meeting rails, and between them there is a gap. It is small, but on older windows it is enough.

A thin flexible blade, a palette knife or similar, slides into that gap and makes contact with the fastener. The catch rotates on a pivot, and a blade pushed against it in the right direction rotates it open. The window is then free to slide.

This takes seconds, requires no specialist tool, causes no damage, and leaves no visible sign of entry. It is one of the oldest entry methods there is and it still works on any unmodified sash window.

Older fasteners are worse.

Decades of paint layers, worn pivots and loose fixings all increase the play in the mechanism, which makes the blade method easier rather than harder.

Brighton style fasteners are better but not sufficient.

Some period homes have fasteners with a screw down locking collar. These resist the blade method considerably better than a plain fitch catch, and they are still not a lock.

What Actually Secures a Sash Window

Keyed sash locks.

These fit to the meeting rail and throw a bolt from the inner sash into the outer, independent of the fastener. Released only with a key from inside, they cannot be reached or rotated with a blade through the gap. This is the direct answer to the blade method.

Sash stops.

A bolt fitted into the upper sash stile that engages a hole in the outer sash, limiting how far the window can be raised. Fitted at two positions, a sash stop allows the window to be opened a few inches for ventilation while preventing it opening far enough to climb through. For bedrooms and rooms that need airflow, this is often more useful than a lock that forces a choice between closed and vulnerable.

Dual screws.

A simple and traditional solution. A threaded bolt passes through both meeting rails and is tightened with a removable key. Inexpensive, discreet, effective, and sympathetic to period windows where visible modern hardware is unwanted.

Laminated glass or security film.

Addresses the break and reach route rather than the blade route. Worth considering where a sash window sits adjacent to a door lock.

Which Windows to Prioritise

Ground floor windows out of public view.

Rear and side elevations screened by fencing or planting give cover, and cover is what makes a quiet blade entry attractive.

Windows accessible from garden structures.

A first floor sash reachable from a garage roof, a wall or a pergola should be treated as a ground floor window.

Sash windows adjacent to doors.

Where reaching through gives access to a door handle or thumb turn.

Less urgent.

Upper floor windows with no access route, and windows directly overlooking a street where anyone working on them is visible.

The Period Property Consideration

Many Bayside homes with original sash windows have genuine heritage value in the joinery and existing hardware. Security upgrades on these windows need to be chosen with that in mind.



Dual screws and sash stops are both minimally invasive and largely concealed. Keyed sash locks are available in finishes sympathetic to period hardware. None of these require modification to the sash boxes, cords or weights, and all are reversible.

The Fire Egress Point

Any window designated as an emergency escape route must remain openable from inside without a key. Where keyed sash locks are fitted to bedroom windows, the key needs to live in a consistent, accessible position known to everyone in the household, close to the window but not reachable or visible from outside. Sash stops are often the better choice in bedrooms for exactly this reason, since they restrict opening without locking the window shut.

Frequently Asked Questions

  • Can sash locks be fitted without damaging original windows?

    Yes. Dual screws and sash stops require only small drilled holes in the meeting rails or stiles and are reversible. Keyed sash locks surface mount to the meeting rail. None affect the sash boxes, cords or weights.

  • Will security hardware stop my sash windows from opening properly?

    No. Sash stops limit travel deliberately but allow partial opening for ventilation. Keyed locks and dual screws are released from inside and the window then operates normally.

  • How many locks does one sash window need?

    One keyed lock or dual screw secures the window closed. Adding a pair of sash stops as well allows secure ventilation. For most ground floor windows, a lock plus stops covers both requirements.

  • Are sash windows less secure than modern casement windows?

    Unmodified, yes, because the standard fastener is defeated so easily. Fitted with appropriate secondary locking, a sash window reaches a comparable level to a modern window with keyed locking.

  • Does my insurer require window locks?

    Some policies specify key operated locking on accessible windows as a condition of cover. It is worth checking your policy schedule, since fitting them is inexpensive and the consequence of not meeting a stated condition can be significant at claim time.

Contact True Locksmith on  0421-767-767   for window lock assessment and installation across Bayside Melbourne. Neale works regularly with period sash windows in the area and fits security hardware that suits original joinery while meeting fire egress requirements. Over 30 years of experience. MLAA member and VIC Police registered. Serving Sandringham, Brighton, Brighton East, North Brighton, Beaumaris, Bentleigh, Black Rock, Caulfield, Cheltenham, Hampton, Highett, McKinnon, Mentone, Moorabbin, Mordialloc and Parkdale.