On all fours locked in a stockade like this one with a large diameter dildo mounted on the rod. Spiked parachute harness tied back to the upright so you can't move forward as a dildo goes in. The 2.5" diameter dildo is then inserted about 5" into your ass and the rod locked in place. You can't move back to ease your balls without driving the dildo further in and you can't move forward off the dildo. Clover style nipple clamps are tied downwards to the frame under tension to further restrict movement. Moving in any direction causes pain but holding motionless rapidly becomes unbearable too.

It was suggested that lubing the dildo with cinnamon or ginger oil would add an extra dimension to the experience. eek

https://www.extremerestraints.com/stockade-with-optional-fucking-rod.html