QR code

From Nookipedia, the Animal Crossing wiki

QR codes can be used to share designs with other players in Animal Crossing: New Leaf. The player can do this by first becoming friends with Sable, who is located at the Able Sisters. Once accomplished, a green sewing machine will appear right behind her. If the player talks to Sable, she will ask if the player would like to create or scan a QR code. If the player chooses to create a QR code, they can select one of their own designs to have a QR code made for it. If the player scans one, the player will receive the design from the scanned QR code, which will be placed in one of the player's pattern spots.

Scannable Designs