This instrument is made up of four small brass bars, pivoted and hinged to make a folding rule.If two of the bars are folded correctly, a triangle is formed, at the vertex of which hangs a plumb-line, allowing slopes to be measured or levelled with the aid of the degree scale marked on the first bar.
The instrument was intended for military uses, to determine the heights of fortresses and escarpments. Although the instrument is unsigned, the style in which it has been made suggests that it was constructed in Germany, probably by Christoph Schissler.