Blend flour and shortening until the size of a pea. Set aside. Break egg into a container and beat. Add enough water to egg to make 1 cup, mix in vinegar and salt. Add this to the flour mixture and blend with a fork. Seal dough in a plastic container. Use as needed. Dough keeps in refrigerator for 2 months. Makes 3 two crust pies or 6 one crust pies.