Choose either 1 inch or .75 inch shells. Place dashed lines over previously marked shells to mark from the bottom of an area up. Align center mark on shells at base of previous row of shells to mark from the top of an area down. For concentric circles or fans, secure pivot hole using a push pin, place pencil point in larger hole and swing tool to create first arc. Move pencil desired spacing, and swing tool back to draw next arc.