The present invention relates to an interlocking coupling system (1) for overhead aligned rails (4, 5) of which at least one rail (4) is displaceably arranged and comprises a first coupling part (2) and a second coupling part (3), each of said coupling parts (2, 3) is arranged at end parts of said rails (4, 5) and arranged for interlocking, when said rails (4, 5) are in aligned position, wherein each of said coupling parts (2, 3) comprises a pivotal gate member (23, 33), and said first coupling part (23) comprises a locking bolt member (21) with a tapered end part (214) adapted to engage with a pin (334) projecting from said gate member (33) of said second coupling part (3) and said locking bolt member (21) is adapted to engage with a recess (234) in said pivotal gate member (23), and both said gate members (23, 33) are activated by displacing said locking bolt member (21).