Consists of a mobile frame of metallic tubing, mounted on two datum wheels, respect to which the irregularities are determined. A probe wheel is mounted in the line of datum wheel. Movement of the probe wheel is taken to the pointer through a sprocket wheel. The pointer moves over a graduated dial. Handles are provided at either end of the frame for easy operation. As the instrument is moved along a line on the test surface, the probe wheel undulates with the undulations in the test surface leading to electric buzEKEng whenever the unevenness exceeds the set value. Automatic spraying of colour is done at locations where the unevenness is larger than the preset maximum value. The extent of bumps (protrusions and depressions) is instantaneously indicated by the pointer on the dial.