Envelope moisteners apply water evenly to adhesive flaps so you can seal envelopes cleanly without licking them by hand. Available in sponge-tip, roller, and electric styles, they suit everything from occasional office mail to daily mailroom batches. Note that peel-and-seal envelopes don't need a moistener at all, since only moisture-activated adhesive requires one. Electric and roller styles add speed and consistency for larger batches, while a simple sponge-tip model is usually enough for occasional use. If you're sealing larger volumes regularly, an envelope sealer can save even more time.