Abstract: Various systems for advancing medical devices within a subject's body are provided that configured to engage the outer surface of the medical device at a number of points about the circumference of the medical device, to thereby grip the medical device for enabling advancement of the device. The advancing systems include engaging portions configured to engage the outer surface of a medical device at a number of points about the circumference of the medical device. The engaging portions preferably engage opposing sides of the medical device's outer surface over a predetermined longitudinal length, to clamp against a longitudinal portion of the medical device that provides improved surface contact with the medical device over conventional roller guides. Various methods for performing medical procedures utilizing various medical devices and advancer systems are also provided.