Preheat oven to 450'F.
Sift flour, salt, soda, and baking powder into mixing bowl. Cut in shortening, using 2 knives, a pastry cutteror your hands dusted with flour. Add sufficient buttermilk to make a soft dough. Knead lightly and turn out onto a lightly floured board. Roll out to 1/2" thickness and cut with biscuit cutter into rounds. Place rounds not touching - for crisper biscuits - or close together - for softer biscuits - on ungreased baking sheet. Brush with melted butter if desired and bake in preheated oven 12-15 minutes, or until firm and lightly browned.