This stitch involves a third loop on the hook. You need to work two chain (see page 17) for the turning chain at the start of a row of half treble crochet.
1 Yarn over hook before you insert the hook into the next stitch.
2 Insert the hook in the next stitch, from front to back (see page 24). Yarn over hook.
3 Pull the loop through the stitch only. There should be three loops on the hook.
4 Yarn over hook again.
5 Pull the loop through the three loops on the hook to complete one half treble crochet. Work one half treble crochet in the same way into every stitch across the row.