An introducer device for a medical implant comprising a plurality of components for performing a sequence of steps to introduce the medical implant into a desired location and deploying it there wherein selected ones of said components are interconnected by a respective catch arrangement (142) whereby, when one component (104,106,136) has reached a first desired location (150) relative to another component (100), the catch arrangement automatically engages to resist withdrawal of said one component from its first desired location, and when said one component has reached a second desired location (152) relative to the other component, the catch arrangement automatically engages to resist withdrawal of said one component from its second desired location, characterised in that the first desired location is a temporary location and the second desired location is a final location, and in that the catch arrangement engages in a stronger manner at the final location than at the temporary location.
