The aim of our work is the development of image analysis tools and methods for the investigation of drawings and drawn drafts in order to investigate the authorship, to identify copies or more general to allow for a comparison of different types of drawings. It was and is common for artists to draw their design as several drafts on paper. These drawings can show how some elements were adjusted until the artist was satisfied with the composition. Therefore it can bring insights into the practice of artists and painting and/or drawing schools. This information is useful for art historians, because it can relate artists to each other. The goal of this paper is to describe a stroke classification algorithm which can recognize the drawing tool based on the shape of the endings of an open stroke. In this context, "open" means that both endings of a stroke are free-standing, uncovered and do not pass into another stroke. These endings are prominent features whose shape carries information about the drawing tool and are therefore used as features to distinguish different drawing tools. Our results show that it is possible to use these endings as input a drawing tool classificator.