Duplex and Triplex paper technique is the procedure of machine bonding two or three sheets of paper together to form a thicker paper board.  These papers may have the same or different quality and become one solid layer by following a specific procedure. The final product is inflexible since it has a duple or triple thickness of a simple paper.

This technique should be applied for three reasons:
1) to increase the thickness of the papers, commonly available at the market
2) to use two different kinds of papers, with different texture in the same business card
3) to apply different post-printing procedures in each side of the paper without them interfering

This paper technique can be accomplished before or after the special post-printing procedures and it is most commonly used in business cards, book covers, and invitations.