This stitch makes drops one or two rows below the row your working on resulting in a “spike”.
How to Crochet the Back Post Double Crochet Stitch
This technique is a variation of the double crochet but instead of going into the top of the stitch we actually go around the post of the stitch underneath.
Crochet 101: How to Crochet the Double Crochet Stitch
The double crochet stitch is one of the most common crochet stitches. It is a taller stitch than single crochet.