FPdc: Yo, insert hook from front to back to front around post of next st of row below, yo and draw up a lp, [yo and draw through 2 lps on hook] twice.

BPdc: Yo, insert hook from back to front to back around post of next st of row below, yo and draw up a lp, [yo and draw through 2 lps on hook] twice.

(ch a multiple of 2 sts + 3)
Foundation Row dc in 4th ch from hook and in each ch across. Turn.
Row 1 Ch 3 (counts as 1 dc), skip first dc, *1 FPdc around next st of row below, 1 dc in next st; rep from * to last st, 1 FPdc around next st of row below, 1 dc in top of t-ch. Turn.
Row 2 Ch 3 (counts as 1 dc), skip first dc, *1 BPdc around next st of row below, 1 dc in next dc; rep from * to last st, 1 BPdc around next st of row below, 1 dc in top of t-ch. Turn.
Rep rows 1 and 2.