A tool holder for a modular tool is provided in which the tool holder may be releasably coupled to a working part such as a rasp, reamer or impactor. The coupling comprises a slot closed at both extremities, and widening to an entry aperture at one extremity, into which a keyed element of the tool may be inserted, and slid to the opposite extremity of the slot. The modular tool defines a securing pin channel through its body, terminating at the entry aperture such that a securing pin inserted into the channel block the entry aperture and locks the keyed element of the tool in place once inserted.