the inboard buckle for a four - way seat is attached to the seat through a variable buckle guide . attaching the inboard buckle to the seat allows the buckle to move with the seat and obviates the need for a long buckle which introduces undesirable slack into the seat belt system during a crash event . since the buckle moves with the seat , it remains in a location that is convenient for the occupant and provides the maximum occupant protection . the variable buckle guide is attached to the upper rail supporting the seat , and in a crash event , the variable buckle guide transfers the occupant load on the belt to the upper rail , avoiding distortion of the seat or the height adjusting levers supporting the seat , and thus precludes slack in the belt caused by such distortion .