Cast on 48, 2x2 for 16 rounds.
Pattern 10 rounds. Start thumb on rnd 11, Inc to 21 thumb sts, place 19 on holder.
Work 20 rounds more in pattern (50 pattern rounds total).
2x2 for 8 rounds, bind off.
Pick up thumb, plus 3, dec 2 sts on first round, 1 more round plain. 2x2 for 8 rounds, bind off.