The half double crochet comes halfway between a single crochet and a double crochet in height.
1. Skip first 2 chain stitches.
2. Yarn over hook once.
3. Insert hook from front to back in the center of the third chain from the hook.
4. Yarn over.
5. Draw the yarn through the chain.
6. There are 3 loops on hook.
7. Yarn over.
8. Draw through 3 loops on hook.
9. One half double crochet has been formed.