This disclosure includes techniques for securing the proximal ends of a medical lead to the connector block of an IMD with a fastener device that incorporates a flexible clamp. A fastener device for a medical device comprising a flexible clamp forming a clamp aperture, wherein the flexible clamp includes a clamp protrusion configured to facilitate actuation of the flexible clamp, a rigid body, wherein the rigid body connects to and surrounds the flexible clamp, and an actuator configured to actuate on the clamp protrusion to change a perimeter of the clamp aperture, wherein the change of the perimeter of the clamp aperture by the actuator is configured to apply a compressive force about a perimeter of an electrical contact of a medical lead in the clamp aperture to electrically and mechanically connect the medical lead to the fastener device.