Connect to SURFCAM. Set up the Locked Plane environment in the Locked Plane Settings dialog in the Options menu. Define the initial plane in space corresponding to the first plane in the area to be digitized. Define the number of planes and the distance between them. After setting up the proper environment, begin the digitizing session by selecting Digitize menu item in SURFCAM. A small dialog will appear on the screen, which allows the user to make all the multiple planes active, or to select an individual plane among the set of planes. To begin taking points, position the digitizer tip near the first point to be digitized, and then hold down the primary button. Move the digitizer tip to cross the defined locked plane(s). When a plane is crossed by the tip, a point is digitized. Release the primary button to stop taking points, and press the secondary button to delete the previous point. Planes can be selected individually from the set of planes by using the small dialog that appears in Locked Plane mode. The digitizing session is terminated when another menu item in SURFCAM is selected.