A technique of graphic representation which makes it possible to assess the degree of similarity between collections of tools or groups of sites. Along the horizontal x-coordinate are arranged the tools or characteristics in question, in accordance with a defined order corresponding to the type list of the collections or sites. On the vertical y-coordinate their relative frequency is plotted. The diagram appears as series of steps each of which conveys the relative numerical importance of each tool or characteristic added to the relative frequency of the elements which precede it in the type list.