A malleable tube is assembled to a rigid fitting by placing the end of the tube over one end of the fitting which has a barb with a locking face facing away from the end of the fitting and a sloping face facing the end of the fitting, the tube is gripped with jaws which have an inward nose projection of a small axial extent and this nose projection grips the tube at about the end of the fitting, force is applied between the fitting and the jaws to relatively move the fitting and tube longitudinally into the jaws until the nose projection has relatively moved past the barb on the fitting.