Abstract: A device for loosening and tightening threaded caps on the neck of bottles and bottle-like containers, the device having a body with a conically widening inner cavity dimensioned to accommodate the customary bottle cap sizes. On the inner surface of the cavity there is a thread with a pitch the direction of which is opposite to the direction of the pitch of the thread of the bottle-cap. By the aid of the thread the device is pressed onto the cap and loosens it on the bottle neck when the device is screwed onto the cap in its opening direction.