How to Install a Cat Door in a Door

Most DIYers can handle the job with basic tools, but the process hinges on one thing: cutting with the door off its hinges and laid flat. That step makes the difference between a clean, square opening and a splintered mess. Whether you’re fitting a simple flap for a hollow-core interior door or cutting through solid wood or metal entry doors, the core sequence stays the same.

What You’ll Need Before You Start

Gather everything before removing the door.

• Template supplied with the cat door kit
• Tape measure, pencil, and a level
• Drill with appropriately sized bits
• Jigsaw or sabre saw (metal-cutting blade for metal doors)
• Screwdriver and the kit’s screws or binder posts
• Safety glasses, dust mask, and ear protection

Measuring and Marking the Door

Measure your pet’s shoulder height and stomach-to-floor distance. Most manufacturers recommend the bottom of the flap opening sit roughly 2 inches (5 cm) above the floor, so your cat steps through naturally. Mark that height, draw a vertical centerline down the door’s face, align the template to your marks, and tape it firmly. Check with a level — a crooked cat door binds the flap.

One rule matters most: keep the cut at least 3 inches from any door edge. Cutting closer risks weakening the structure, and on hollow-core doors you can blow through the thin outer skin. If your pet’s height forces the opening too close to an edge, consider a different mounting spot or a smaller model.

Removing the Door and Cutting the Opening

Pull the hinge pins with a hammer and screwdriver, then lay the door flat across two sawhorses. This gives better control, a straighter line, and keeps sawdust off your floor. Drill starter holes in the corners — These give the jigsaw blade room to turn corners cleanly.

Cut along the inside of your pencil lines, moving slowly and letting the blade do the work; forcing it can splinter the veneer. Sand or file the cut edges smooth, then test-fit the frame before fastening. On metal doors, swap in a metal-cutting blade and plan extra steps: deburr edges, apply rust-inhibiting primer, and seal with silicone caulk. On exterior doors, PetSafe’s guidance calls for clear weatherproof caulk around the exterior frame as well.

Fitting the Frame and Rehanging the Door

Insert the outer frame half from the exterior side and the inner half from the interior side, then snap or screw them together. For PetSafe 4-way locking models: secure the middle frame, then snap the interior frame onto it. Tighten screws snug — PetSafe’s large cat door instructions warn explicitly against over-tightening.

Drill pilot holes before driving screws into wood. For hollow-core doors, only screws hitting the solid frame around the cut will bite — two good screws are enough, per the guide.

Test the flap’s swing and lock position before rehanging. Then lift the door back onto its hinges and drop the pins in. Your cat will usually investigate within minutes.

What About Glass Doors and Sliding Panels?

Cutting through a glass door yourself is not a DIY job — A cracked pane is a bigger expense than a professional cut. For sliding glass doors, a vinyl insert panel like the Endura Flap is practical: loosen height-adjustment locks, slide the panel into the upper track, engage the spring mechanism, and tighten locks. Check panel thickness first —

If weighing options before buying, our tested roundup of the best electronic cat doors covers models with locking timers and microchip readers that keep strays out.

FAQs

Can I install a cat door without removing the door from its hinges? You can, but it’s harder and riskier. Cutting on sawhorses gives a stable surface, contains sawdust, and lets you position the jigsaw at the right angle. Removing the door also prevents the saw from vibrating loose hinges or damaging the frame.

What size hole do I need for a cat door? The size depends entirely on your model — there is no standard dimension. The template that ships with the door is the only reliable guide. Most are printed at 100% scale, so tape it in place and trace exactly along its lines.

How do I install a cat door in a hollow-core door? The process is the same as solid wood, but only a few screws find solid material along the internal frame. Drill pilot holes and drive screws gently — over-tightening can crush the hollow interior and bulge the door’s surface.