Tape can be utilised to seal an envelope or container. Both pressure-sensitive and gummed tapes are appropriate for sealing and strengthening envelopes and packages. These may be made of plastic, cloth, or paper.
The United States Postal Service states that tape must be applied correctly for the best results. A gummed tape requires sufficient hydration. The surface must be clean and at a temperature above freezing, as freezing temperatures might cause the tape to shatter. Pressure-sensitive tape can be applied to cold surfaces, but following application, it must be rubbed down.
Cellophane and masking tape cannot be utilised to seal an envelope. These tapes may only be utilised to reinforce another closure, such as a self-adhesive envelope.