There is disclosed a driver including an elongate shaft and at least one drive assembly. The drive assembly includes a housing which has an orifice for receiving the elongate shaft, and a drive wheel which is located at least partially within the housing. The drive wheel has a bore with a cross-section shaped so that the internal surface of the bore contacts the circumference of elongate shaft when the elongate shaft is inserted into the bore. The bore has at least two fulcrum surfaces so that the drive wheel is pivotable about the elongate shaft. The housing is slideable relative to the elongate shaft.