The Delta Bes-Align 4 x 4" Adjustable Lens Board, calibrates lenses for maximum sharpness, as well as checking for fall-off, lens distortion, edge sharpness, and parallel alignment.
The board adjusts front to back, left to right with three control knobs. A test negative is included for calibration, with the 4 x 4" lens board.
The Bes-Align may require a retaining ring, depending on the lens.