Abstract: A tool (1) for a tool holder (3) of a blister packing machine. The tool (1) comprises a body member (25) extending from a proximal front end (30) to a distal rear end (32) and defines a major engagement face (27) for abutting a corresponding abutment face (5) of the tool holder (3), and an opposite major working face (29) which acts on the material to be worked on by the tool (1). An elongated alignment member (35) extending from a proximal end (40) to a distal end (42) extends centrally along the body member (25) from a location adjacent the proximal end (30) of the body member (25) towards the distal end (32). The alignment member (35) is of T-shaped transverse cross-section having a central member (37) and a pair of side flanges (39) extending from the central member (37) for slideably engaging a corresponding T-shaped receiving groove (10) in the tool holder (3).