A karabiner (10) comprises a body portion (12) and a gate portion (16) which is mounted to the body portion about a pivot (18), the gate (16) defining a free end (20) which is arranged to inter-engage with a nose (22) of the body portion to define a closed ring for receiving a rope (50) passing therethrough and including a first sleeve (26) which, when the ring is closed, is moveable between a first position where the gate is free to rotate about the pivot in at least one direction, and a second position where the sleeve at least partly encloses the free end of the gate and the nose and substantially prevents rotation of the gate about the pivot, and further including a second sleeve (28) which is internally threaded and which is mounted on an externally threaded portion (30) of the gate for movement towards and away from the free end of the gate and which may be rotated towards the first sleeve when the first sleeve is in the second position, to prevent movement of the sleeve into first position in which the gate is free to rotate.