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Installing a Pet Door in Glass

A pet door is a great way to allow your dog or cat the freedom to come as they please, freeing up your time spent playing doorman. Pet doors aren’t just limited to the classic door and wall mount; there are plenty of other installation options—including through glass installations!

Installing a pet door in glass is perfect for those who want a low-impact installation, sans the drilling, cutting, and handiwork. In this article, we’ll walk you through the ins and outs of pet doors for glass, including:

cat using endura flap sash window

Pet Doors for Windows

Installing a pet door in your window is a quick, easy, no-tools-needed process. It’s an excellent choice if you don’t want to obstruct your sliding door in any way. Window pet doors are quite versatile, with options for both side-sliding windows and sash windows.

For Sash Windows: Endura Thermo Sash 3e Pet Door

The Endura Thermo Sash 3e Pet Door fits sashes 22” - 43” wide, with a spring-loaded adjustment piece built in 3” increments. The adjustment piece allows you to fit the panel into your sash window in a matter of minutes without any tools.

For Side-Sliding Windows: Endura Horizontal Sliding Window Cat Door

The side-sliding window panel works in the same way as the sash panel, but vertically. You pop the panel into the window track and use the adjustment piece at the top to extend it into the top of the track for a snug fit. Because of the size limitations, this panel is for cats or very small dogs only with a 6” x 11” flap.

Check out our fill selection of pet doors for windows for more options. And read more about why the Endura Flap is great for cats, too!

Pet Doors for Sliding Glass Doors

Pet doors can also be installed in sliding glass doors. The simplest option for this location is a patio panel with a pre-installed pet door. This panel pops into the sliding glass door track, taking up some of the space used for humans to walk through. It installs in just a few minutes without any tools. Depending on your sliding door, we have both aluminum and vinyl options, as detailed below.

For Aluminum Sliding Doors: Endura Flap Thermo Panel 3e

thermo panel 3e

The Thermo panel 3e is an excellent choice for installing a pet door in a sliding glass door. The panel has dual-pane, Low-E glass to keep your home insulated year-round. For something lighter and more portable, check out the Endura Quick Panel 3. It has the same Endura Flap door, but uses single-pane glass. Read about dual-pane vs single-pane glass here for more details.

For Vinyl Sliding Doors: Endura Vinyl Sliding Dog Door

For vinyl-framed sliding doors, we recommend a vinyl-framed patio panel for the most secure, aesthetic fit. You can read about aluminum vs vinyl sliding doors here. The Endura vinyl sliding dog door works for sliders with tracks at least 1.5” thick, and installs in just a few minutes. The vinyl is nice and lightweight, making it a great option for vacation homes and rentals. 

For a shorter vinyl slider, see the Custom Severe Weather Vinyl Sliding Glass Dog DoorTake a look at our full list sliding glass pet doors for more options.

Installing Directly Through Glass

The Endura flap cannot be installed directly through existing glass, as cutting the glass would shatter it. To work around this, we have the In the Glass pet door. This is a full sheet of glass with a pre-installed Endura flap pet door. This sheet replaces the existing pane of glass from your slider, French door, window, or sidelight. It can pretty much be installed anywhere there is glass in your home.

The In the Glass requires a glazier to come and measure your glass so that the custom-size pane can be built for you. Then, your glazier comes back to replace your existing pane of glass with this new one--much like they might replace a broken window or glass door. The In the Glass is made with dual-pane and Low-E glass, so it will keep your home insulated in harsh weather.

Benefits of the In The Glass Door:

  • Hands-off process; your glazier measures and installs
  • Does not obstruct the sliding door
  • Allows you to use your existing door or window lock

Locking Pet Doors for Glass

If you want the pet door to mate with your existing lock, we recommend the In the Glass, as it only replaces the glass unit so that your door still functions with its usual frame and lock. You can learn more about the differences between the In the Glass and Patio Panel pet doors here.

For glass doors and sideways-sliding windows, your pet door panel will come with a C-clamp lock to use in the track. For additional security, we recommend a wooden dowel or Charley Bar.

For sash windows, a Charley bar or wooden dowel is an excellent choice. You can also install a wood screw in the window track directly above the sash for a permanent lock. Read more about security concerns for pet doors here.

Elizabeth Muenzen

Written by

Content Specialist

Pets: My dog Benji is mixed Yorkie, Poodle, Chihuahua, and MaltiPom (YorkiPooChiMaltiPom?), yet he mysteriously bears no resemblance to any of these breeds.
Fun stuff: I love to cook!

Content Specialist

Pets: My dog Benji is mixed Yorkie, Poodle, Chihuahua, and MaltiPom (YorkiPooChiMaltiPom?), yet he mysteriously bears no resemblance to any of these breeds.
Fun stuff: I love to cook!


  • Hi Cathy,

    Here is the Endura Flap Replacement Flap page:

    Please feel free to contact us at 800.826.2871 or if you have any questions!

    Elizabeth (Staff)
  • Hi Sue,

    Please feel free to contact us at 800.826.2871 or and we can help you find the best option for your sliding glass door. Look forward to hearing from you!

    Happy holidays!

    Elizabeth (Staff)
  • Hi
    I’m enquiring about a doggy door for a glass sliding door and would like to know the best option please.

  • I need a replacement flap for my dog door that is 25X15”

    Cathy Hare

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