Oh, you are not the only one who comes back and makes a wrong cut--I can't count the number of times I have done this. I have found the stuff that sticks on the ruler at the desired measurement, it comes on a roll and is about 1/4" wide. For the life of me can't remember the name and tossed the packaging. Its a bright color though so you can see where the measurement should be. Maybe someone else can help with the name of the tape.