Envelopes are used to dispatch important material, so details like a secure flap and seal are vital.

There are many ways to seal an envelope. The simplest is with glue, which may need moisture to work while some are self-adhering with light pressure. Some gums can also be reused to close the envelope. Peel and stick envelopes are becoming more popular. A thin strip of paper is peeled off then the gummed area is pressed for sealing the envelope. More ready-made seals are also available such as buttons, clasp, snap and zips. Buttons and metal or plastic clasps are common in heavier paper envelopes while snaps and zips are available only on plastic envelopes.

There are seals that create an elegant envelope for invitations, weddings, thank you notes etc. They come in a wide variety of colors for all occasions. They can be embossed or simply printed in a variety of symbols or themes. Their text, font and colors can be personalized for individual needs to a large extent. Generally they are around one inch size and can be ordered via Internet or can be picked up from a stationary shop.

Traditional sealing wax is still in use. Some use a wax sticks along with a wooden stamp handle. Drip melted wax onto the envelope and press with the wooden stamp handle to imprint the design. This unique method is not very commonly used.

Another popular mode of envelope seals is the perforated edge. These are popular with tax information, some bills, even with online DVD rental stores.