Independent Sector: The part of the economy consisting of non-profit organizations. Also called the Non-profit Sector.
Indicia: A unique printed artwork box in the top right corner of an envelope, authorized by the post office, indicating that postage has been paid by the mailer.
Ink-Jet Printing: Process performed by lettershop to quickly print donor name, address, keycode and other variable data on each piece of mail.
Insert: See Package Insert.
Involvement device: An element in a direct mail fundraising package that donors peel off, sign, cut out or handle with their hands in others ways. Involvement devices can boost response, and include surveys, petitions, stamps and stickers.
