Cut a square out around the perimeter of the tear. Make the square as small as possible, while still cutting the entire tear out. Achieve straight lines using a carpenter’s square. Cut the carpet with a utility knife, cutting through carpet, but leaving the padding behind. Remove the cutout piece of carpet. If necessary, use the end of a putty knife to pry the carpet up.
Cut a piece of cardboard to 1 inch larger than the cutout section. Pull the edge of carpet up around the hole you just made. Insert the cardboard inside the hole and under the carpet. If necessary, fold the cardboard slightly to get it into the hole.
Trace the hole onto the cardboard, staying as close to the edge of the hole as possible. Remove the cardboard. Cut the traced shape out using the utility knife. Use the carpenter’s square to keep the lines straight.
Turn a carpet remnant upside down. Trace the cardboard cutout on the back of the carpet piece. Cut it out using the utility knife and carpenter’s square to create a patch.
Cut a piece of double-faced seam tape to fit inside the hole. Apply the seam tape to the carpet padding inside the hole. Place the patch from Step 4 inside the hole. Press down to adhere it to the tape.
Run a vacuum over the patched area to blend the carpet fibers together, hiding the patch.