Combine rolled oats, flours, and salt. Cut butter into dry ingredients until coarse-textured. Add water, one tablespoon at a time, to form a dough that just holds together. Add a little more water, if necessary.
Turn onto a lightly floured smooth surface. Roll to ⅛-inch thickness. Cut into 2½-inch squares or use a cookie cutter to cut into 3-inch circles.
Bake on an ungreased cookie sheet at 375ᵒ F. for 12 to 15 minutes or until lightly browned. Cool on wire racks. Store in a tightly sealed container to retain crispness.