An electronic design guide, such as a french curve, can be placed in the geometry layer of a drawing program. This allows the design guide and a drawing tool, such as an electronic paint brush, to be moved about with in the drawing simultaneously using two different input control devices, such as a mouse and an electronic stylus/tablet. The design guide can then be used block or mask paint from being applied to the drawing by comparing the coordinates of the cursor with the area of the guide and setting pixels of the drawing accordingly. The masking can be performed even as the guide is moved. The system also can be set to constrain the path of the ink applied by the drawing tool to the edge of the drawing guide even as the guide is moved. As the cursor is moved the position of the cursor is matched with the closest next line segment of the guide and that portion painted.