A guide wire locking mechanism for a catheter system includes a motion-limiting component adapted to contact a portion of a guide wire and limit the direction of motion that the guide wire can slide therethrough. The motion-limiting component allows the guide wire to slide in one direction when placed in the locking mechanism but prevents the guide wire from moving in the opposite direction. The motion-limiting component can be made from a row of movable teeth having contact surfaces or faces which come in contact with a portion of the guide wire. The teeth are bendable to allow the guide wire to move in one direction but will tighten against the guide wire if one attempts to move the guide wire in an opposite direction.