A method for testing a prosthetic heart valve leaflet is provided. The method includes using a vertical post having a longitudinal axis and a horizontal bar having a bar-axis that lies on a vertical bar-plane. The bar supports the leaflet along the bar-axis such that the leaflet drapes over the bar. A linear actuator movably couples the bar to the post, and actuation of the actuator moves the bar vertically in the bar-plane. A light source emits a beam of light and is oriented to direct the beam through the bar-plane. A gauge measures an elevation of the bar above the beam. A detector is positioned to detect the beam and generates a detection-signal indicative of detection of the beam. Other applications are also described.