I call these scissors: Hang from the bar in an "L", and go from straddle to pike keeping your legs perpendicular to your body. You can also intersperse it with leg lifts, chin-ups, and other various bar exercises.
We also do straddle-L and L-holds on P-bars, beam, floor, and uphill straddle-L's as well.
2. Inclined sit ups.. so your feet on a height, legs bent in 90 degree shape
3. Sit on the edge of a table, feet hanging off the end, place an ankle weight around the ankle,and bring your knee up to the ceiling
4. Lying down (on table), bend one leg, have other leg straight with ankle weight on it, raise your straight leg up only to a comfortable height
(don't let weight touch the table.... make sure knee is straight of leg with weight on it)