Installing a small pet door into a removable storm window, rather than a door, is a great way to allow your cat access to the outdoors without the permanence associated with installation in a door or wall.

Step 1: Remove one of the glass storm window panels from a ground-level window. Choose a window that faces into the back yard or onto a covered porch.

Installing a pet door into a storm window, rather than a door, is a great way to allow your cat access to the outdoors.

Step 2: Remove the glass from the storm window and have a piece of 1/8-inch-thick acrylic sheeting, commonly referred to as Plexiglas, cut to the same size as the window glass.

Step 3: Position the pet door installation template on the Plexiglas several inches above the bottom edge. Following the template, trace the opening of the pet door onto the Plexiglas.

Step 4: Use a Plexiglas cutter to score the outline into the Plexiglas. Continue scoring the outline until the Plexiglas rectangle can be pushed out of the storm window. It may be necessary to drill small holes into each corner of the template outline and use a plastic-cutting bit on a Rotozip or a Dremel tool to facilitate the removal of the scored piece of Plexiglas. Be careful not to crack the Plexiglas too much. Plexiglas is brittle; it may take a second try with a new piece of sheeting to accomplish the goal.

Step 5: Once the opening has been made in the Plexiglas, install the sheet into the storm window frame.

Step 6: Follow the manufacturer’s directions and install the small pet door onto the storm window. Be sure to install the outer portion of the frame on the outside face of the storm window and the inner portion of the frame on the inside of the window.

Step 7: Reinstall the storm window into the lower portion of the window opening.

Step 8: Position something beneath the pet door to facilitate access to the opening on both the inside and the outside of the home.

Step 9: Control access to the pet door by opening and shutting the actual window, rather than moving the storm window.

Step 10: Teach your pet to use the door by opening the pet door and offering treats each time it enters and exits through the opening. Once the pet is comfortable going through the opening, repeat the process with the door portion closed.

— Linda Cottin can be reached at LawrenceLiving@ljworld.com.