Abstract: In a catheter (10) with wings (26,27) which are brought into a retaining disposition by pulling on a distal tip insert (11) with an actuating means (16) manipulated from the proximal end of the catheter, the retaining surfaces (10B,31) move freely into their co-operative holding disposition from a transport disposition because they are spaced from one another in the transport disposition. The actuating means (16) is preferably a trocar and has a sleeve (19) which not only drives the catheter into position but also controls liquid flow down the catheter tube. Stop surfaces (29,10C) prevent "overshoot" of the wings past the desired retaining disposition and make more positive the disengagement of latching surfaces (22,23) between the tip element (11) and the trocar (16).