Stir together flour, baking powder, and salt. Cut in shortening with fork until mixture resembles coarse corn meal. Add milk and blend lightly with fork only until flour is moistened and dough pulls away from sides of bowl. Turn out on lightly floured board. Knead lightly (30 seconds) and roll ¾ inch thick. Cut dough with biscuit cutter, dipping cutter into flour between cuts. Place on lightly greased pan and brush tops of biscuits with butter or margarine. Bake at 475 (very hot oven) for 12 to 15 minutes.