Sift the flour with the salt. Cut in the shortening until the mixture looks like small peas. Cut in the butter coarsely. The addition of the butter makes a flaky pastry crust.
Sprinkle this mixture with water a tablespoon at a time and mix lightly with a fork. Keep adding water 1 tablespoon at a time, just until dough will come together when you mix it with the fork.
Gather the dough into a ball. (The dough can be refrigerated until ready to use at this stage). If using the pie dough now, divide the pastry into 2 sections, one just slightly larger than the other. Take the larger ball of dough and roll it out into a large, thin circle with a rolling pin. Make sure you sprinkle a bit of flour on the surface you are rolling the dough out on before you begin. Use the larger sheet of dough as the bottom crust of a 2 crust pie. Roll out the other piece for the top.
Follow directions on the pie recipe for how to bake the pie.