This one is quite self explanatory but the sadist inside of you wants to hear how it was used, right? The device is a square shape with two wooden blocks on either side and two layers of spikes in the middle. The block was put over the knee of the victim so that there was a layer of spikes behind and at the front of their knee. The screws were then tightened together until it completely closed making their knee pretty much crack and break. Grim.