A secure open window sounds like a contradiction. Windows are either open or secure. That binary has defined home security for decades, and it forces UK homeowners to choose between fresh air and peace of mind whenever they leave a window cracked. One product category breaks that binary by locking windows in the open position. LockLatch® was invented in South Africa, patented internationally (UK patent EP2989274, SA patent 2014/09494, USA patent 9,797,173), and proven across more than two decades in one of the world’s most demanding home-security environments before it reached the UK market.
Why a Secure Open Window Matters Year-Round
Most people first hear about LockLatch® in summer, when indoor temperatures climb and bedrooms become difficult to sleep in. That is the obvious season for safer ventilation. But a surprising share of UK customers buy LockLatch® for winter use too — for letting condensation escape the bathroom and kitchen overnight, for keeping the air moving in a closed-up house, and for letting pets come and go through a side window or door without leaving the whole house exposed.
The product family grew organically from real customer feedback. LockLatch® came first, designed for the standard adult-sized window or door gap of 9 to 17 centimetres. Dog owners then started asking whether their pet could fit through. The honest answer was that it depended on how big the dog was. PetLatch® was developed for that exact use case — a wider 14.5 to 23 centimetre gap that lets a medium or large dog come and go through a door. Then a friend in Durban mentioned a vervet monkey problem and asked for a shorter version that would let air in but keep monkeys out. That became MonkeyLatch, later renamed MiniLatch® (4.5 to 8 centimetres) once UK and international orders started arriving for child safety, cat safety and cooler-weather ventilation. Three products, one engineering platform, a full range of gap widths.
What Makes a Window Secure When Open?
Three things. The window must be held at a fixed gap that cannot be widened from outside. The mechanism holding it must be rigid enough to resist force. And the mechanism must be lockable so it cannot be released without authorisation.
LockLatch® meets all three requirements. It is a C304 rust-resistant stainless steel arm that holds any window at an adjustable gap of 9 to 17 centimetres. A locking pin drops into the barrel of the lock in any of the four holes, and the lock is lockable with a removable key. The window stays open. The window stays locked.
The device fits any window or door whatever the frame is made from and whichever way it opens. Casement, sash, sliding, top-hung, awning. Timber, uPVC, aluminium, steel. That universality is why a single product covers the entire UK housing stock.
Pets Are at Least 40 Percent of the UK Market
UK pet owners treat their cats and dogs like family. Their safety and comfort matter more than convenience or cost. Across LockLatch® UK customers, pet-related installations make up a significant share of the market.
- Letting dogs come and go without making a mess indoors. A side window or back door secured at a 14-17cm gap with PetLatch® lets a small or medium dog access the garden without the house being unsecured.
- Same for cats. A LockLatch® on a sash or casement gives a cat a regular route in and out at a gap too narrow for an intruder.
- Keeping indoor cats safely in, and keeping neighbours’ cats out. MiniLatch® at its 4.5-8cm range provides ventilation but stops cats squeezing through in either direction.
- Preventing falls from upper-floor windows. High-rise feline syndrome is a recognised veterinary issue. Cats see an open window as an opportunity. MiniLatch® holds the window at a gap a cat cannot pass through, while still allowing fresh air into the room.
For UK pet owners, the value is in safety and convenience, not the unit price.
Target Hardening: Why Resistance Sends Burglars Moving On
Crime prevention specialists describe a concept called target hardening. The principle is that opportunistic intruders move on when they encounter resistance. They are not carrying specialist tools. They are testing handles, pushing windows and looking for the easiest route in.
A lockable pin secures the LockLatch® arm in position. The window cannot be pushed further open without removing the device, and the device cannot be removed without the key. That level of resistance is enough to send an opportunistic intruder to the next house. This is target hardening in practice — changing the risk profile of a window from easy to difficult, and inviting the chancer to move on.
Claire from Hungerford in the UK contacted LockLatch® after a break-in at her property. The intruder attempted to enter through her patio sliding door, which was secured with a LockLatch®. Rather than defeat the lock, the intruder broke the window pane itself, cut himself in the process, was caught, charged and sentenced. Her insurance assessor inspected the LockLatch® and accepted it as a secure lock. The standard UK rule still applies — when premises are unoccupied, windows and doors should be closed and locked — but Claire’s story shows what target hardening looks like in real life.
How Much Airflow Does a 9 to 17 Centimetre Gap Provide?
Industry guidance for residential ventilation recommends a minimum opening of around four litres per second per person for bedrooms. A 9 centimetre gap across a standard 600mm-wide window provides approximately 15 litres per second in a light breeze of 2 metres per second. That is nearly four times the minimum requirement.
At the maximum 17 centimetre setting, airflow roughly doubles. The adjustable range means homeowners can calibrate the gap to the conditions: smaller on windy nights, larger on still ones. In winter, the same range allows controlled airflow for damp control and condensation management without leaving the house wide open.
The effective opening is slightly narrower than the nominal range because the footplates usually mount to the middle of the frame rather than the very edge, reducing the usable gap by approximately 3 to 4 centimetres. This still exceeds the minimum ventilation requirement comfortably.
No Tradesman Needed
The installation is a 15-minute DIY job. Four small holes are drilled into the frame, then secured using either a screwdriver or a rivet gun depending on the frame type. One-way security screws on wood and steel frames, pop rivets on uPVC and aluminium. No specialist tools beyond a drill.
This matters more than it sounds. Letting an unfamiliar tradesman into the home introduces its own security risk: an unknown person sees the layout, the alarm system, the window that will receive the new lock, and which keys are kept where. For a security product specifically, doing the install yourself removes that risk entirely. The homeowner remains the only person who knows where every LockLatch® is fitted and how it operates.
If the product is ever removed, the holes can be covered with rubber grommets or filled with wood filler or silicone for a permanent finish.
Battle-Hardened in South Africa, Refined for the UK
LockLatch® was designed in South Africa, where break-in rates per capita are among the highest in the world and homes balance security against extreme summer heat. For more than two decades, South African homeowners have used LockLatch® to keep windows open at night for cross-ventilation while the family sleeps, knowing the window cannot be pushed wider from outside.
The product that arrived in the UK is the same one that survived 20-plus years of real-world testing in that environment. The C304 stainless steel arm, the lockable pin, the four-hole mount, the adjustable gap range — all refined under conditions far more demanding than the average UK street. The international patents (UK EP2989274, SA 2014/09494, USA 9,797,173) protect a design that has been quietly proven before being brought to a wider market.
Worldwide Delivery
LockLatch® ships from distribution centres in South Africa and the UK. The UK distribution centre is in Penley, near Wrexham, with delivery across England, Scotland, Wales and Northern Ireland typically taking two to four working days via Royal Mail or courier. Beyond the UK and South Africa, LockLatch® ships worldwide via Royal Mail and international couriers — customers in Europe, North America, Australia, New Zealand and the rest of the world receive the same product, the same lifetime guarantee and the same C304 rust-resistant stainless steel construction.
Shop LockLatch® now and secure your windows in the open position year-round.
