Pet doors come in many different shapes and sizes. Most are designed to be mounted into a 1 1/2- to 2-inch-thick door. Some are made to be mounted into sliding patio screen doors or through exterior (or interior) walls. With the right tools, installing a pet door can be a relatively easy project.

Step 1: Measure the pet’s height and width to determine the correct size of door. Choose a door that meets both the pet’s size requirements and the mounting requirements for the project.

Step 2: Determine the correct height to mount the door by measuring from the floor to the bottom of the pet’s chest. If the ground level on the outside is different from the floor level on the inside, split the difference of the two heights and subtract that number from the pet’s chest height. This is the distance the bottom of the pet door should be above the higher of the two ground levels. Draw a horizontal line to mark the spot on the existing door, wall or screen.

Step 3: Tape the mounting template that came with the pet door onto the surface where the door is to be mounted. Make sure the bottom of the door is centered and leveled against the horizontal line drawn in step two.

Step 4: Use a power drill to drill pilot holes completely through each of the template corners.

Step 5: Use a jig saw to cut the opening of the door by inserting the jig saw blade into the pilot hole. Cut up from the bottom of the opening to the top on both sides and then cut over for the top and bottom.

Step 6: Set the pet door into the opening and mark the spots for each mounting screw.

Step 7: Remove the pet door and use a power drill to drill pilot holes for the mounting screws.

Step 8: Once the pilot holes have been drilled, re-insert the pet door and mount it properly, according to the manufacturer’s instructions.

Step 9: Run a bead of exterior caulk around the edges of the pet door on both the inside and outside door panels to prevent any air loss or moisture infiltration.

Introduce your pet to its new portal to the great outdoors and use positive reinforcement to encourage its use until the pet is comfortable with the new door.