Apparatus (20) for testing a prosthetic leaflet (10) includes a bar (22); a light source (24); a detector (26); an actuator (40); a gauge (28); a display (82); and circuitry (84). The leaflet is draped over the bar. The light source emits a beam of light (32). The detector detects the beam, and generates a detection-signal indicative of detection of the beam. Actuation of the actuator moves the bar with respect to the beam. The gauge measures an elevation of the bar above the beam, the elevation changing with the moving of the bar by the actuator. The circuitry is configured: (i) to receive the measured elevation from the gauge, (ii) to receive the detection-signal from the detector, and (iii) in response to the detection-signal, to drive the display to display the elevation that was measured when the detection-signal was received by the circuitry.