Fenster Glazing
Cat and Dog Flaps
A sealed glass unit cannot be cut once it has been made. So a flap in glass means a new unit with the hole already in it, and a flap in a door panel is one we cut ourselves. Working out which of those two your door needs is the first thing we do, because it decides the rest of the job.
Key specifications
Cat and Dog Flaps
- Flap types Standard or microchip
- Fitted into Glass or door panel
- Glass route A new sealed unit
- Approved installer SureFlap
Pet flap fitting
Glass or panel decides the rest of the job.
A sealed glass unit cannot be cut once it has been made. So a flap in glass means a new unit with the hole already in it, and a flap in a door panel is one we cut ourselves. Working out which of those two your door needs is the first thing we do, because it decides the rest of the job.
Two flaps, not a catalogue
A standard flap that you lock by hand when you want it shut, or a microchip flap that reads the chip your pet already has and opens only for them. The second one is what people ask for when someone else's cat has been letting itself in.
Glass means a new unit
Toughened and sealed units cannot be cut after they are made, which surprises most people. We measure the opening, order a new unit with the aperture already in the right place, and fit the flap into that.
Panels we cut ourselves
Where the door has a panel that suits it, we cut the aperture and fit the flap into it. We check the material and the thickness first, because not every panel will take one.
It does not have to be our door
We fit flaps into doors and windows that are already in the house, not only into ones we are making for you. If we did not install it, we will still tell you straight whether it will take a flap.
Approved SureFlap installers
We are approved to fit SureFlap, and we fit other makes as well. That means the flap gets chosen around your pet and your door rather than around one brand.
Two flaps, not a catalogue
A standard flap that you lock by hand when you want it shut, or a microchip flap that reads the chip your pet already has and opens only for them. The second one is what people ask for when someone else's cat has been letting itself in.
Glass means a new unit
Toughened and sealed units cannot be cut after they are made, which surprises most people. We measure the opening, order a new unit with the aperture already in the right place, and fit the flap into that.
Panels we cut ourselves
Where the door has a panel that suits it, we cut the aperture and fit the flap into it. We check the material and the thickness first, because not every panel will take one.
It does not have to be our door
We fit flaps into doors and windows that are already in the house, not only into ones we are making for you. If we did not install it, we will still tell you straight whether it will take a flap.
Approved SureFlap installers
We are approved to fit SureFlap, and we fit other makes as well. That means the flap gets chosen around your pet and your door rather than around one brand.
Went through it. Came back. Went through it again.
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How it actually goes in
Two ways in, and the door decides which.
From the outside a pet flap looks like a hole in a door. The part that matters is what it is being cut into: a sealed unit that has to be remade, or a panel we can cut on site. We look at the door, the pet and the outside step before anything is ordered.
Check my pet flap optionsInto new glass
A sealed unit cannot be cut once it has been made, so we measure the opening and order a new unit with the aperture already in it. The old unit comes out, the new one goes in, and the flap fits into that.
- The glass you have cannot be cut
- Aperture made at the factory
- Usually a week or two for the unit
Into a door panel
Where the door has a panel that suits it, we cut the aperture ourselves and fit the flap straight into it. We check the material and the thickness first, because not every panel will take one.
- Cut by us, on site
- Suitable panels only
- No glass to reorder
Standard or microchip
The standard flap locks by hand when you want it shut. The microchip flap reads the chip your pet already has and opens only for them, which is the one people ask for when other animals have been getting in. Either goes into glass or a panel.
- Both lock
- Microchip reads your own pet
- We are approved SureFlap installers
Where it sits
Height matters more than people expect. We look at the pet, the threshold and what is on the other side, because a flap at the wrong height gets used once and then ignored.
- Set around the pet, not the door
- Outside step checked
- Cats and dogs, sized to suit
Product guide
More information on Cat and Dog Flaps
A sealed unit cannot be cut once it has been made, so a flap in glass means a new unit with the aperture already in it. A flap in a door panel is one we cut ourselves. We work out which of the two your door needs before anything is ordered, on doors and windows that are already there as well as new ones.
Glass fitting
A new sealed unit made to order with the aperture already in it, usually a week or two
Sealed glass cannot be cut once it has been made, so we order a new unit with the aperture already in the right place.
Panel fitting
Cut by us on site, where the panel material and thickness suit it
We cut the panel ourselves, once the material and the thickness have been checked. Not every panel will take a flap.
Flap types
A standard flap that locks by hand, or a microchip flap that opens only for your pet
A standard flap locks by hand. A microchip flap reads the chip your pet already has and opens only for them. Either goes into glass or a panel.
Survey checks
Pet size, flap height, glass type, door construction, threshold and outside access
Pet size, outside access, threshold height and how the door is built all decide where the flap should sit.
Product questions
FAQs about cat and dog flaps
Can you fit a cat flap into a double glazed door?
Yes, but not by cutting the glass you already have. A sealed unit cannot be cut once it has been made, so we measure the opening and order a new unit with the aperture already in it. The flap goes into that. Dog flaps and microchip flaps go in the same way, with a bigger aperture for a dog.
Can you fit one into a door panel instead?
Yes, where the panel suits it. We cut the aperture ourselves and fit the flap into the panel. We check the material and thickness first, because not every panel will take one.
What is the difference between the two flaps you fit?
A standard flap locks by hand when you want it shut. A microchip flap reads the chip your pet already has and opens only for them, so other animals stay outside. Both go into glass or a panel the same way.
Does it have to be a door you installed?
No. We fit flaps into doors and windows that are already in the house, as well as into new ones we are making for you.
How long does it take?
Glass is the longer of the two. The new unit is made to order with the aperture already in it, so allow a week or two from the survey. A panel does not need a new unit made, so it is normally quicker.
Pet flap process
We look at the door before anything is ordered.
A pet flap is not made to survey sizes like a window, so the order goes in once we know which route your door takes and which flap you want.
Look at the door
We work out whether the flap is going into a panel we can cut, or into a new sealed unit, because that decides the rest of it.
Pick the flap
A standard flap that locks by hand, or a microchip one that opens only for your pet. We size it around the animal rather than the door.
Order the part
A new glass unit is made to order with the aperture already in it, so allow a week or two. A panel does not need one.
Fit and finish
We fit it, weather it and check your pet can actually get through at the height it has ended up.
What Milton Keynes homeowners say
Real reviews from real installations. Every one is public, so you can go and check them yourself.
Stuart Matthew
7 months ago
Fenster have just completed a front door installation on my new property - fantastic job and strongly recommend! The online design tool is great, Perry back at HQ is brilliant as is his communication. Andy, who installed the door, is a top gent and professional. Will definitely be a returning customer.
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Joanna Hayes
2 months ago
Really happy with the service we received from Fensters Windows. Aaron and Shane turned up on time and were both really friendly. They explained any issues as they went along and talked us through the different options, which we really appreciated. They did a great job fitting our new back doors and cleaned up everything afterwards. We also paid exactly what we had originally been quoted, with no unexpected extra costs. Really pleased with our new doors and would definitely recommend Fensters Windows. Thank you Aaron and Shane!
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Digger
2 months ago
We have used Fensters for years on a variety of glazing work, and 2 door installations. They are competitively priced and responsive. They take great care over measuring and specifying the work, giving you a clear quote so you understand what you are getting (thanks Perry!). The fitters are all extremely competent and personable. We had to replace our front door for accessibility reasons, they gave us confidence that our requirements would be met, reproduced the intricate leaded and stained-glass pattern of our old door, and did a quality fitting job (thanks to Johnnie and Shane!). In summary they are our go-to suppliers for all replacement and repair work.
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Silvia Peraro
a month ago
I had an excellent experience with Fenster Glazing from start to finish. Nick Perry and David managed the initial quote to installation process seamlessly, keeping communication clear, honest, and completely stress-free. When it came to the actual fitting, Zac and Shane did a fantastic job with the installation, working efficiently and leaving everything spotless. The professionalism from the entire team was top-notch, and the final result looks brilliant. I highly recommend them.
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Bernie Raffe
3 months ago
Great service from Fenster Glazing, very happy with our new bi-fold door, glass door and windows (with built-in blinds) There was an issue with the wrong spec of glass provided to them from their supplier, so they had to temporarily board up a door and a window, but this was put right within a few weeks. Recommended, thanks.
Read on Google Zak Jessup 12 Jun 2025Cannot recommend higher! Nick and Perry were really helpful in getting my windows sorted ASAP.
Read on Google Norman Cummings 10 Jun 2025The best service ever, great workmen, very high standard and in the finish, excellent eye to detail.
Read on GoogleOur work
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