A locking device for a maintaining an elongated member at a selected place within a body lumen includes a substantially rigid body including an attachment portion adapted to be coupled to a proximal portion of a medical instrument. When in an operative position, the distal portion of the medical instrument is received within the body lumen and a head coupled to the substantially rigid body. The head is configured to overlie an access port of the medical device when the attachment portion is coupled to the proximal portion of the medical device in a predetermined configuration. A plurality of locking features extends from the head to immobilize a section of the elongated member relative to the medical device.