A method and apparatus is provided whereby a shadow mask support pin can be forced into a cathode ray tube panel without having to use any panel support post. Three or four support pads are utilized to support the bottom edge of the skirt portion of the panel. Each of the support pads may be elevationally moved by a drive unit. First through fourth distance sensors serve to detect the height of corner points on the interior surface of the panel face portion. A control device is adapted to control the operation of the drive unit in a manner that the corner points are brought into a predetermined reference plane before the support pin insertion proceeds. A fifth distance sensor may be further employed to detect the height of a center point.