The half double crochet (abbreviated hdc) is kind of an oddball stitch. The half double crochet falls in between a single crochet and a double crochet in height, but instead of working off two loops at a time, you draw the yarn through three loops on the hook. It produces a fairly tight fabric similar to one made with a single crochet stitch:
Do 15 chain stitches (ch 15).
This step creates the foundation chain.
Chain 2 more stitches.
These stitches create the turning chain.
Yarn over the hook (yo) and insert your hook in the third chain from the hook.
See the illustration.
Yarn over the hook and gently pull the wrapped hook through the center of the chain stitch, carrying the wrapped yarn through the stitch.
You should have 3 loops on your hook.
Yarn over the hook and draw your yarn through all 3 loops on your hook.
See the image for a demonstration.
Begin in the next chain of the foundation chain.
This step completes a full row of half double crochet stitches.
Work 1 half double crochet stitch in each successive chain across the foundation chain.
You have 16 half double crochet stitches at the end of Row 1 (counting the turning chain as 1 half double crochet stitch).
Turn your work.
You need to turn your work to start Row 2.
Chain 2 (ch 2) and yarn over the hook (yo).
The two stitches are for the turning chain.
Skipping the first stitch of the row directly below the turning chain, insert your hook in the next stitch.
Skipping the first stitch maintains a consistent number of stitches per row.
Repeat the preceding steps in each of the next 14 half double crochet (hdc) stitches.
Follow the steps from pulling the wrapped hook through the center of the chain stitch to drawing yarn through all 3 loops.
Work 1 half double crochet in the top chain of the previous row’s turning chain.
You should have 16 half double crochet stitches in Row 2 (counting the turning chain as 1 half double crochet).