The Hoffman's Test is a special test I use all the time to help identify, central cervical spine stenosis.
The test is performed by holding the patient's middle finger and stabilizing the distal ip joint and with the nail of your index finger of the other hand, "flick" the patient's nail in a palmer direction.
The test is positive if the patient's index finger and/or the thumb approximate toward each other such as what you see in this video.