A fastening unit for attaching a horizontal first beam to a second beam, said second beam being a vertical standard, via a locking collar, wherein said second beam is arranged substantially perpendicularly to said first beam, said fastening unit having a first axis and a second axis, wherein said second axis is substantially perpendicular to said first axis, said fastening unit comprising: a connecting member extending in a direction parallel to said first axis of said fastening unit and having a first edge portion, a second edge portion and a central portion, said connecting member further comprising a coupling element, wherein said coupling element is arranged to be attached to said first beam; said fastening unit further comprising a locking head, said locking head comprising a first leg and a second leg extending substantially parallel to each other in a direction parallel to said first axis of said fastening unit, said first leg comprising an outer portion and an inner portion (8"), and a first through opening running in a direction parallel to said second axis of said fastening unit between said outer and said inner (8") portions of said first leg, said second leg comprising an outer portion and an inner portion (9"), and a second through opening running in a direction parallel to said second axis of said fastening unit between said outer and said inner portions (9") of said second leg, said locking head further comprising an stopping member running in a direction parallel to said second axis of said fastening unit and interconnecting said first and said second legs (8, 9) of said locking head, said locking head comprising a receiving cavity arranged between said inner portion (8") of said first leg and said inner portion (9") of said second leg and being delimited at an inner end by said stopping member, said receiving cavity being arranged to receive said locking collar; said fastening unit further comprising a locking wedge, which is permanently connected to said locking head and is movably arranged inside said first through opening, said locking wedge comprising a leading portion arranged at one end of said locking wedge, and a gripping portion at the other end of said locking wedge; wherein said locking head is movably attached to said connecting member, said locking head is movable in a direction substantially parallel to said first axis relative said connecting member between a first end position and a second end position, and that said gripping portion of said locking wedge is in contact with said connecting member when said locking head is in said second end position, characterized in that the movable connection between the locking head and the connecting member is provided by means of a fastening member extending through said connecting member and said locking head. a connecting member extending in a direction parallel to said first axis of said fastening unit and having a first edge portion, a second edge portion and a central portion, said connecting member further comprising a coupling element, wherein said coupling element is arranged to be attached to said first beam; said fastening unit further comprising a locking head, said locking head comprising a first leg and a second leg extending substantially parallel to each other in a direction parallel to said first axis of said fastening unit, said first leg comprising an outer portion and an inner portion (8"), and a first through opening running in a direction parallel to said second axis of said fastening unit between said outer and said inner (8") portions of said first leg, said second leg comprising an outer portion and an inner portion (9"), and a second through opening running in a direction parallel to said second axis of said fastening unit between said outer and said inner portions (9") of said second leg, said locking head further comprising an stopping member running in a direction parallel to said second axis of said fastening unit and interconnecting said first and said second legs (8, 9) of said locking head, said locking head comprising a receiving cavity arranged between said inner portion (8") of said first leg and said inner portion (9") of said second leg and being delimited at an inner end by said stopping member, said receiving cavity being arranged to receive said locking collar; said fastening unit further comprising a locking wedge, which is permanently connected to said locking head and is movably arranged inside said first through opening, said locking wedge comprising a leading portion arranged at one end of said locking wedge, and a gripping portion at the other end of said locking wedge; wherein said locking head is movably attached to said connecting member, said locking head is movable in a direction substantially parallel to said first axis relative said connecting member between a first end position and a second end position, and that said gripping portion of said locking wedge is in contact with said connecting member when said locking head is in said second end position, characterized in that the movable connection between the locking head and the connecting member is provided by means of a fastening member extending through said connecting member and said locking head.