A wrench having two driving stems pivotally connected with each other. In response to receiving a write operation for a block of data on a first volume, a lock is obtained on a corresponding block of data on a second volume to obtain exclusive access to that block of data on the second volume. The attachment mechanism may allow attachment of the elongated body to a gun barrel, a gun magazine, or other gun component. Delivery accumulators are incremented and decremented with delivery requests and with deliveries made. In response to the request, the load balancer joins the other server as a member of the cluster to handle some work requests subsequently assigned to the cluster. Substances other than oil may be remediated as well.