Video 2. Normal motion of the posterior inguinal wall. When the conjoint tendon becomes taught as the internal oblique & transversus abdominis muscles contract, the superior ‘wall’ of the inguinal canal normally moves inferiorly as a ‘shutter’ to protect against herniation of abdominal contents directly through the vulnerable transversalis fascia of posterior inguinal wall. Video shown here was acquired with a broad-band 13-5 MHz linear array transducer orientated in a sagittal-oblique plane to display the inguinal canal in short-axis with the patient’s head to the viewer’s left. Normal shutter motion is shown as the patient contracts the abdominal muscles during a partial ‘sit-up’ manoeuvre: the superior margin of the inguinal canal, appreciated as an increasingly abrupt angulation in wall contour, can be seen to move in an inferior direction. Note the posterior wall of the inguinal canal (indicated by the central segment of the red line) normally shows progressive tilt but remains straight (yellow arrow). Animated overlay courtesy of Missing Mouse Design .