Extended half double crochet (ehdc) is a variation of half double crochet (hdc). To work with ehdc we insert the hook one round below, not in next stitch beside as we work the hdc.
Here is step by step how to make ehdc:
1. Yarn over
2. Insert hook in stitch one round below
3. Yarn over then pull through the stitch. You have 3 loops on hook.
4. Yarn over and pull through 3 loops on hook.
You can use ehdc with other crochet stitch to make your work more beautiful.
Happy crocheting 🙂