What is a seatbelt grip?

The seatbelt grip is the standard control from back position - one arm over the shoulder (choking arm) and one arm under the armpit, hands connected across their chest like a seatbelt. This grip controls their upper body and sets up rear naked chokes. The overhook arm prevents them from turning toward you, while the underhook arm stops them from turning away. Maintaining a tight seatbelt is essential for keeping the back position.