Abstract: The device for securing the hull of a watercraft and/or a sailboat mast comprises a locking bar the lower end of which has a hook, an annular eyelet or a crosshead by means of which the locking arm can be secured on a portion of the roof carrier which supports the hull of the watercraft and is secured to the roof of an automotive vehicle or on the sailboat mast which can be inserted between the roof and the roof carrier during transport. The upper end of the locking bar has a thread onto which can be screwed a flange or nut by means of which the hull of the watercraft or the sailboat mast can be securely clamped. The threadedly connectable flange or nut acts either upon the hull of the watercraft, e.g., a surfboard, or upon a portion of the roof carrier when the sailboat mast is secured by the locking bar. If this safety device is to be used in connection with the hull of a watercraft, it is necessary that the hull be provided with a through opening, for example, a daggerboard opening.