All you need:
        A window
        One Command strip
        A Plastic cutting board or placemat
        A dowel (for security)

package of command strips

Command strips are awesome. They have so many uses. (Check out a gallery of all the ones I use around my house -future link here)

Where to start: Figure out which window to use for the cat door and how big it needs to be, which will depend on the size of your kitty. If the window has a screen you will need to remove it. Keep it some place safe, where it won’t rip easily, in case you ever need to put it back; especially if the house is a rental. Open the window only as wide as necessary for your pet to get through – no wider. Trim the plastic cutting board or placemat to fit the size of the opening.

flexible plastic cutting mat
You can find these at the dollar tree!

Optional: For a little extra security, cut a sturdy dowel and place it in the window frame so the window won’t easily open any further then needed.
Read the instructions on the command strips, they’re pretty basic and easy to follow.

window with command strip attached to the top of frame
cat door in window

When placing the Command strip place it on the outer rim of the window frame – as shown – not inside the track. That way you’ll still be able to close the window.
Anytime you need to close the cat door, you just close the window.

Next, attach the trimmed plastic to the command strip. So simple!

kitty cat using window cat door

There you have it,
hassle free, low cost, and removable. The easiest and best pet door ever!