English: Diagram showing the two steps of testing for shifting dullness.

Step 1. Percuss along the abdomen away form the midline (following the red line) until it produces a dull note (green section) Marking this area with your finger. Step 2. Roll the patient towards you wait enough time for any free fluid (blue in diagram) to move and now percussion should result in a resonant note.

To finish of return patient to supine position and confirm position is now dull.