A catheter assembly includes a pull wire and a control member subassembly, wherein the pull wire is secured to a post of the subassembly that may extend through a slot of a handle, and an engagement feature of the subassembly, being supported by an elastically deformable support of the subassembly resting on a railway of the handle, confronts a mating feature of the handle to interlock therewith, responsive to the support being un-deformed. The post, engagement feature, and support may be integrally formed together in a single-piece component, wherein the engagement feature may be one or two rows of teeth formed in a surface of an upper portion of the component, and the support may be a pair of flexible cantilever beam members of a lower portion of the component. Furthermore, the mating surface and railway may be integrally formed in an inner surface of a shell of the handle.