Bottom line: Used to localize loss of hearing perception and conduction by applying vibrating fork to midline of patient’s skull.
See Fig. 7-16A for visual of where to place vibrating fork. -The Head and Neck. In: DeGowin’s Diagnostic Examination. (AccessMedicine.)
Weber Test (Wikipedia) includes a table that summarizes how the findings of the Weber and Rinne tests can be used to screen patients for sensorineural versus conductive loss and localized left or right.
Bates guide has a short video showing how to conduct Weber test. It starts about ¾ of the way through the Examining the Ears video.