The Alpine Astronomical Baader T-2 Locking Ring is used to prevent other parts of the Astro T-2 modular accessory system from moving out of position after they are put in their proper place—such as to prevent a part from moving after you have set it to the correct back focus distance. You simply screw the ring against the other part to lock it in place. Use the ring's lever when there is not enough room for your hands or fingers to properly manipulate it, or to give you more leverage to break the connection when you want to disassemble the rig.