A routine test object used for beam alignment and centring in radiography and fluoroscopy.
A special variant of the vertical bucky jig is available for Siemens’  Vertix system.

Measure:
• The correspondence of the light field with the effective radiation field
• The determination of the position of the central beam
• The central beam angle deviation from 90°, relative to the plane of the film/detector, is below a limit beyond which the image quality would be adversely affected