Diagonal Square

The Spruce: https://www.thespruce.com/how-to-crochet-diagonal-square-4056331

Diagonal Square
Diagonal Square

Corner-to-corner crochet, also known as diagonal crochet, diagonal box stitch and c2c, is a method of starting crochet in one corner of a square, growing it row by row on the diagonal until you reach the desired size and then decreasing back down to the opposite corner. The stitches, made with double crochet, look very similar to the granny stitch, but the way that the rows are turned and worked on the diagonal give it a slightly different, more interesting, texture.