Artist Trading Cards or ATC are little works of art measuring exactly 3.5 inches tall and 2.5 inches wide. They are usually swapped.

https://www.tinteddy.com/introduction-to-atcs-what-are-ar...

The patterns are for pockets to slip your cards in.

Both pockets are easy to make using both knit and purl stitches.

Size approx 9x 8 cms