For small screen devices, such as PDAs, which totally depend on a pen-based user interface, traditional menu-selection/button-clicking based user interface becomes inconvenient for graphics inputting. In this paper, a novel sketch-based graphics inputting user interface is presented. By sketching a few constituent primitive shapes of the user-intended graphic object, the candidate graphic objects in the shape database are guessed and displayed in a ranked list according to their partial structural similarity to what the user has drawn. The user can then choose the right one from the list and replace the sketchy strokes with the exact graphic object with proper parameters, such as position, size and angle. This user interface is natural for graphics input and is especially suitable for schematic design.