An armrest attachable to a tool to provide support for a worker's wrist while the tool is being manipulated or actuated. The armrest underlies the worker's forearm so the weight of the tool is borne partly by the worker's fingers and hand and partly by the worker's forearm. Stress on the wrist is minimized and good wrist posture is maintained. Due to the location of the armrest, the worker's forearm is located directly behind the tool handle where it can absorb kickback forces that occur as an incidental part of a lockbolt installation process.