Abstract: A power tool comprises a drive shaft (16), a tool (20) for engaging a threaded bolt fastener (22) and marking means (30) for marking the threaded fastener after it has been tightened onto a compatibly threaded hole. The marking means (30) comprises a marking stylus (41, 42, 45, 48, 49) that is moved reciprocally into and out of contact with the fastener, and supply means (62, 63, 61) for supplying a predetermined quantity of liquid marking medium to the stylus for discharge therefore onto the fastener with each cycle of linear movement of the stylus.