as fig3 shows the cylindrical chamber 4 is separated from the interior cylindrical volume of the spigot 3 by a toroidal rib 5 defining a cylindrical passage having an inside diameter adapted to have the distal end 21 of the male end fitting 20 pass through it the cylindrical chamber 4 is able to receive two o rings 22 separated by an o ring spacer ring 23 and a locking ring 24 notched axially at its periphery so as to be engaged forcibly in the chamber 4 and fixed therein flush with the opening of the chamber 4 to facilitate reading of the drawing the components 22 23 22 24 are shown separately but it is to be understood that once assembled they bear one on another the male end fitting 20 passes through the toroidal members 22 24 as its flange 25 bears in the vicinity of the locking ring 24 or even bear on it a shoulder not shown may be formed in the cylindrical cavity for fixing an abutment for locating the locking ring 24 the body 2 includes externally and toward its front portion an enlargement in the form of a square platform 30 with upstanding opposite low walls 31 a pillar 40 rises toward the front of the body 2 from the two opposite sides of the platform 30.