The fitment (12) is fixed detachably without tools on the connecting part (1) by swivel tension elements (8) such as levers. When swivelled, the tension elements change the outer dia. of dowels (4) held in recesses. The levers can have a U- or L-shaped cross-section and rotate or swivel about a swivel path less than 180 deg.. The levers can be locked in several positions. When turned in, the levers are covered wholly or partly by the fitment.
