Half double crochet
US hdc is UK half treble (htr). One final draw-through passes through all three loops.
Counted practice swatch
Chain 17; begin in the third chain from the hook for 15 hdc. The two skipped chains do not count as a stitch in this sample.
Work the repeat
Yarn over, insert under the two top loops, yarn over and pull up a loop. Yarn over and pull through all three. Later rows: ch2, turn and hdc in the first and every following stitch.
Read the fabric
Count 15 worked tops after each row. The third loop sits behind the usual V; enter the top V unless the pattern names another loop.