Fiat 2016 500X Owner's Manual page 226

224 SAFETY
2. Grasp the mini-latch plate and pull the seat belt over
the seat.
Pulling Out The Latch Plate
Inserting Latch Plate Into Buckle
3. Route the shoulder belt to the inside of the left head
restraint.
4. When the seat belt is long enough to fit, insert the
mini-latch plate into the mini-buckle until you hear a
"click."