Fold the seat-back forward, then recline the seat-back to the first lock position, and adjust the headrest to the highest position.

Apply masking tape on the top of the headrest.

Make marks (A) on both sides at 250 mm (9.84 in.) upward from the roots of the headrest frame (B) along the back of the headrest (C) surface. Make a center of these points as a datum point (D).