How to Crochet Spikes
Long stitches produce a spike on both sides of the fabric, so they’re well suited for a design that’s reversible. Long stitches (or spikes) are usually single crochet stitches that you work into either the tops of stitches or spaces between stitches one or more rows below the current row, creating a vertical spike of yarn that extends over several rows of stitches.
Insert the hook from front to back under the top two loops of the designated stitch one or more rows below.
This example goes three rows below.
Draw the yarn through the stitch and up to the current level of work.
Don't pull the yarn tight, or your rows will bunch.
Yarn over (yo) and draw the yarn through the 2 loops on your hook.
You've completed a long single crochet stitch (although the length varies depending on where you stick the hook, of course).
To make any type of long stitch, such as a long double crochet, you follow the same steps as for the single crochet. Just remember to yarn over as necessary and then make the stitch the same way you always do. You just stick the hook in a different place.