The floor wiper is an easier variation of the windshield wiper that can be used as an initial step in a progression, or a substitute.
Lie on your back, spread your arms to your sides for a wide base, and bring your straight legs vertically. Slowly rotate to bring your feet to the floor on one side, keeping your legs straight, then back to the other side.
The floor wiper is a more accessible variation of the windshield wiper for training trunk rotation without the added demand of the isometric trunk support in a hanging position.
Sets to maximal reps (not to actual failure) or of 10-20 each direction are typical.
The motion can be slowed down or the feet not allowed to touch the floor to increase difficulty.