Place your tape on the editing block. Pull both ends of tape out of the cassette case. Use your knife to cut off any wrinkled or destroyed tape. Overlap the two ends of tape and cut in the center. Make sure you cut both sides of the tape equally. Your cuts should be neat and precise.
Splice the two ends of tape together using your cellophane tape. You only need to use one piece of cellophane.
Tape your splice together using the cellophane tape. Be sure to only tape on the back side. Putting tape on the front side will damage the tape's sound quality. When finished, carefully roll the repaired tape back into the tape's case.
Take the case apart once you determine the problem. Usually, bunched up tape will cause a tape not to play in the cassette player. Remove the screws of the case using your screwdriver. Or, run your knife blade through the front of the case and open it.
Remove the cassette's cover. Unwind any bunched up tape and rewind it back onto the reel.
Place your new cassette tape's case over the tape. Put the screws in their proper holes and tighten.
Test your newly repaired tape on a cassette player in a playback device to ensure the tape works properly.