When you stick your hand up somebody's ass, grab their tailbone, and lead them around the room - much like steering a sailboat. This can also be done by using a butt plug with a handle on it, but is then called a dutch tugboat.
I put some swifters on Leif's clogs before giving him a Dutch Rudder. Living room floor was clean in about an hour!
When a man masturbates, and another person grabs his arm and makes him do the motion. It's sort of like a cross between masturbation and a handjob. He is still holding on, but the other person is still moving your arm.