Pivotable rollover bar

The device (11) has two vertical supports, each with a pair of bars connected pivotably by a joint with a locking arrangement (17) and a stop. The stop consists of a joint stiffener (15), which consists of an extension of one bar (13) partly enclosing one end of the other bar (12) and the locking arrangement has a continuously adjustable control element with which the joint stiffener can be clamped against the other bar.