Abstract: The force effective in a rope or cable and the stress caused by the force are ascertained by sequentially applying forces (F1, F2) perpendicularly to the rope or cable centrally between two supports. The first force (F1) is applied centrally between two supports contacting the rope or cable at a defined first spacing or distance (g1) from each other to cause a first deflection (h1). The second force (F2) is applied in the same way to cause a second deflection (h2) when the supports have a different spacing or distance (g2) therebetween. The supports during the second force application may be the same as for the first force application, but shifted to a wider spacing or distance (g2). When two pairs of supports are used there is an inner pair of supports between an outer pair of supports and the inner pair can be brought out of contact with the rope or cable when the outer pair is effective during the second force application.