A coupling member includes a hook-shaped coupling part arranged to be hooked into a gripping part of an upright and a locking arrangement switchable between a locking position and a release position. Further, the locking arrangement includes a pivotally attached first clamping part and a wedge-shaped locking part, which is slidable between a locking position and a release position. The wedge-shaped locking part is arranged to push the first clamping part towards the upright and the gripping part by means of wedge action. Moreover, the first clamping part comprises two transversally spaced apart side parts which jointly define a cavity there between. The first clamping part is arranged externally on the hook-shaped coupling part, and is arranged partly within the cavity. Further, each of the side parts includes fastening means for pivotal attachment of the first clamping part to the hook-shaped coupling part.