How to Make a Cat Door with a Magnetic Opener

Select a wall for the cat door that will work well both inside and outside. Use an electric current sensor to make sure the door will not interfere with outlet boxes and wiring.

Measure your car from its shoulder to the floor. Use this measurement for the door height. Next, measure the cat's width from its widest body section. Use this measurement for the door width.

Use a stud finder to locate the stud on the wall. You will need to install the cat door so the left edge is next to the stud.

Remove baseboard molding with a jigsaw. If you do not want to remove the molding, you will need to raise and make a new mark for the height of the door. Measure the height of the baseboard, then raise and mark a new height for the cat door on the wall.

Draw a square or rectangular template on paper according to your measurements for the cat door and cut it out with scissors. Trace the template onto the indoor wall with a marker.

Measure the height inside the wall cavity from the sole plate wood piece on the interior floor to the bottom of your cutout. Cut two pieces of 2-by-4 wood according to your height measurement. These pieces will be used to insulate the interior wall cavity. Use wood screws to attach the base wood blocks to the sole plate.

Trace your template for the cat door opening on the exterior wall. Cut away the sheathing material using a reciprocating saw.

Add up the measurements for the left, right, top and bottom according to your template. Cut a strip of rigid foam insulation according to the total measurement. Score the foam according to your measurements. Fold the foam to create a box shape. Use duct tape to secure the end pieces. Tack the insulation foam box to the wood base piece inside the wall cavity with nails.

Divide the width of the cat door opening by 4. This will be your width measurement for the clear rubber mat strips. Use your height measurement for the height of the strips. Cut eight strips from the rubber mat. You will use 4 strips indoors and 4 strips outdoors. Use contact cement to glue the strips 1 inch from the top of the indoor and outdoor openings.

Cut a magnetic strip according to your width measurements for the opening. Use contact cement to glue the magnetic strips 1 inch above the edge of the rubber mat strips, indoors and outdoors.

Add 1 inch to the width measurement at the top of the cat door, indoors and outdoors. Cut one piece of interior wood molding and one piece of exterior molding, such as vinyl, according to your measurements. Spread beads of contact cement to the molding pieces and glue the molding 1/2 inch above the upper edges of the plastic strips. This will hide the top edges of the strips and help to keep them adhered to the interior and exterior walls.