Mix together flour, baking powder, soda, and salt in a medium mixing bowl. Cut shortening into flour mixture with a pastry blender until mixture resembles coarse meal. Add buttermilk, stirring until dry ingredients are moistened.
Turn dough out onto a lightly floured surface, and knead 4 to 5 times
Roll dough to 1/2-inch thickness; cut with a 2 1/4-inch biscuit cutter. Place biscuits on a greased baking sheet. Bake at 450° for 10 minutes or until biscuits are lightly browned.