Abstract: The upper portion is comprised of an angled metal tube (2) assembled to a cast plastic part (3) having a handle (30) and an arcuate extremity (31) connected by an elongate body (32) the internal face (33) of which assumes the contour of the tube (2) over approximately half the circumference and which has an orifice (37) facing two orifices (22, 23) which are diametrally opposite in the tube (2) and which are facing an orifice (43) provided in a counter-part (4) having one face (42) partially assuming the contour of the tube (2) and an assembly screw (5) enabling the tube (2) to be affixed to the part (3) and to the counter-part (4).