In tool use, a transformation rule defines the relation between an operating movement and its distal effect. This rule is determined by the tool structure and requires no explicit definition. The present study investigates how humans represent and apply compatible and incompatible transformation rules in tool use. In Experiment 1, participants had to switch between tools for which the respective transformation rules were either the same or different. This way, rule repetitions could be dissociated from tool repetitions. In Experiment 2, the application of transformation rules in tool use was compared with the application of explicitly defined rules. In Experiment 3, actions of tool use were cued either by tool pictures or by written tool names. The results suggest that a transformation rule in tool use has a cognitive representation that is independent of the concrete tool incorporating it. Furthermore, its application differs from the application of an explicitly defined rule in terms of reduced top-down processing. (Contains 6 figures.)