Abstract: The device is used for security by e.g the occupier of a hotel room. A toggle-type self-gripping mechanism is provided with thin jaw-blades. The blades are entered into the slot or gap between a door and a door jamb. The jaws engage the door-bolt, and the device enables a heavy gripping clamp to be applied to the bolt. The thin jaws do not buckle under the heavy clamping because they are constrained against buckling by the slot. A screw-clamp may be substituted for the toggle-clamp.