|At Aggregate Industries’ Back Lane Quarry, each guard is now subject to improved security through the use of a sheathed locking nut which requires a specific tool to remove it. With the correct tool, removal is quick and easy. The nut does not necessarily need to be tightened completely, as a retaining nut on the sheath prevents rotation. A protective gromet prevents the ingress of dust. The guard nut tools can be subject to controlled issue, hence allowing management to exercise greater control. The locking guard nuts cost around £1 each and the specialist tool £30-£40. The system is eminently transferable.