Abstract: An endoscopic system having an endoscope carrying an endoscopic medical device that can be an auxiliary rear-ward facing camera or medical tool for cutting, ablation, cutting, suturing, retracting, manipulating, suction, or irrigation. A locking assembly allows the user of the system to lock the rotational orientation of a distal portion of endoscopic medical device within a distal end of the endoscope. The locking assembly has a locking device attached to the distal portion of the endoscopic medical device and a cap that is permanently or removably attached to the distal end of the endoscope. When desired, the user of the system engages the locking device and the cap together to prevent rotation. The locking device can include one more flexible members that can contract when pushed through a working channel of the endoscope and expand to engage mating features on the cap. Magnets can also be used to prevent rotation.