the present invention relates to an interlocking coupling system for overhead aligned rails of which at least one rail is displaceably arranged and comprises a first coupling part and a second coupling part , each of said coupling parts is arranged at end parts of said rails and arranged for interlocking , when said rails are in aligned position , wherein each of said coupling parts comprises a pivotal gate member , and said first coupling part comprises a locking bolt member with a tapered end part adapted to engage with a pin projecting from said gate member of said second coupling part and said locking bolt member is adapted to engage with a recess in said pivotal gate member , and both said gate members are activated by displacing said locking bolt member .