Use the captain's chair for old-school exercises that work the midsection. You can do a variety of routines on this piece of gym equipment, including extended leg raises, bent leg raises, bicycle and side to sides.
Here's one version: Stand on chair and grip handholds. Press your back against the pad, contract your abs and raise your straight legs (option: cross feet at ankles) until you form an L shape. Pause at the top, then lower. Do 2-3 sets for 15-20 reps.