Tip - How to Affix Multiple Stamps to an Envelope | eHow

When sending an envelope through the U.S. Postal Service, you must place sufficient postage on the envelope. If you do not affix enough postage, the post office generally will return the envelope to you; in rare cases, the item will be delivered "postage due:" that is, the addressee may have to pay the shortfall. If one stamp isn't enough...