The present application relates to method of arresting telescopic endwise relative movement in a medical device between an end portion of an elongate member, preferably being a cylinder, and an end portion of a tube, preferably being a cylindrical tube, that receives the end portion of the elongate member. The method is of particular use in the construction of stent delivery systems. In one embodiment, the method comprises providing a length of deformable blocking material; imparting relative endwise movement to draw the blocking material, into the gap and reversing the direction until the blocking material length suffers deformation.