I sat in 343, 733 and 735 jump seats (all LH). There are 5 belts, with the closing mechanism in your navel area (like a spoke, where the 5 pieces join): a lap belt, one going up between your legs, one each over your shoulder.
I was required to wear all five during t/o and landing, but only the lap belt during cruise.
On a side note: I was seated once in a Do 328 1A seat (Team Lufthansa), and the seat belt like in a car, a lap belt and one across your body. I wonder why that is, the other seats were normal.