This invention is directed to a medical device having an elongate shaft having a distal end and a controller coupled to the shaft. A control member can extend through at least part of the elongate shaft and at least part of the controller, wherein the control member in a tensioned configuration can be moveable by the controller to control the distal end of the shaft and the control member can be slack in an untensioned configuration. A tensioning mechanism can be configured to move relative to at least one of the elongate shaft and the controller to tension the control member and automatically lock the control member in the tensioned configuration.