A briefcase is provided with a two-part releasable fastening device, the first part of which includes a movable fastening member for releasably fastening the parts together. The first part of the device further comprises a ball which, when the case is inverted, is urged by gravity into a retaining position in which it prevents releasing movement of the fastening member. When the lid of the case is uppermost, the ball permits movement of the fastening member to release the second part of the device.