Header press-on tools are used to put the headers onto the core assembly. It comes with small medium and large size to fit the header pattern. The header is placed onto the core assembly and the size of the press-on tool for the width of the header is chosen. The press-on tool pushes the header onto the tubes by using the hammer. This is continued down the header to the other end. The tool is made to set the header with a specific distance from the end of the tube. It controls the header to header distance related to the tube length.