The invention relates to a locking device adapted for locking a shutter element (13) adapted to slide along a railing (11), which locking device (3) comprises at least one locking bolt (5) movable between a first state, in which the locking bolt is adapted to engage with a locking member (9) in the shutter element to lock the shutter element against movement, and a second state, in which the locking bolt is adapted to avoid engagement with the locking member and to allow movement of the shutter element. The invention also relates to a locking arrangement adapted to be connected with and allow locking of a shutter element (13) arranged to slide along a railing (11), which locking arrangement (7) comprises at least one locking member (9) shaped to allow a locking bolt (5) to, in a first state, engage with and lock the locking member, and thus the shutter element, against movement. The invention also relates to a locking system.