A lock washer that actually works!
More information here: http://www.nord-lock.com/products/wedge-locking
Nord-Lock wedge-locking products utilise tension to secure bolted joints in demanding industries exposed to vibration and dynamic loads. The system comprises a pair of washers that creates a wedge-effect and prevents the bolt from rotating loose. Achieve and maintain a high and accurate clamp load with quick and easy installation and removal.
A reliable and elegant solution.