The line of thrust is the locus of the points, through which forces pass in a retaining wall or an arch. It is the line, along which internal forces flow, [1], [2].
In a stone structure, the line of thrust is a theoretical line that through the structure represents the path of the resultants of the compressive forces, [3]. For a structure to be stable, the line of thrust must lie entirely inside the structure, [4], [5].