For example, due to the guiderail’s adjustability in length , the spacing between the backrest of the child safety seat and the anchorage point of the third locking mechanism is adjustable in case the backrest comprises the third locking mechanism. It has to be noted here that one may denote this spacing as “dorsal” spacing since from an anatomical point of view of a child being seated in the child safety seat, the dorsal spacing is the spacing behind the child’s back between the backrest and the anchorage point on the back side of the child safety seat.