Describes an apparatus that converts changes in surface topography to changes in strain by passing the surface beneath the end of a beam fitted with a probe. The diameter of the ball forming the probe chosen for the present study was 1/4 in., which was considered satisfactory for studies of finished panels, machined surfaces, and particle boards. Changes of strain are recorded as a continuous graph with adjustable horizontal and vertical magnification up to 400 each way. Evaluation is by reference to the standard deviation of the profile from a line drawn through the graph. Where, in addition to surface roughness, large-scale deviations from the plane, e.g. warp, are present, the base line would be curved. Examples of the application of the apparatus to the testing of planed boards and to veneered panels are given.