Plumbline is used for monitoring horizontal movements in dams, dam foundations, abutments and to determine the structural movements of bridges, piers, towers, and tall buildings.

The Direct Plumb Line of PMT consists of a steel wire anchored at the upper end to the structure, with a tensioning weight suspended at the lower end which is free to move in a tank filled by a damping fluid. A tilt in the structure brings about a shift in the weight which is measured by the readout unit.

The Inverted Plumb Line of PMT provides a fixed datum from which structural movements can be measured. It uses the identical wire anchored in firm soil beneath the structure, with a floating unit fixed to its upper end. The floating unit is free to move in a fluid tank keeping the wire vertically. A tilt or displacement in the foundation brings about a shift in the float which is measured by the readout unit.