The Model 9852 classic corner mount centers the optic at the fourth corner of the square formed with the three adjustment screws, allowing you to get tilt, tilt without translation, and pure translation -- all in a single mount. For pure translation, simply turn all knobs the same amount. (A 1° error in one knob results in only 0.0012° tilt in the face plate.) For tilt without translation, use two knobs, or for applications when translation is less important, adjust the tilt with just one knob.