In a large bowl combine the flour and salt. Cut in the shortening until mixture resembles cornmeal.
In a small bowl combine water, vinegar, and egg. Add egg mixture, a tablespoon at a time, to flour mixture, tossing to form a soft dough. Divide dough into thirds. Shape each portion into a ball. Wrap each ball in waxed paper. Cover; chill for 3 to 24 hours.*
Roll out each portion into a 12-inch circle. Ease into a 9-inch pie plate. Trim to 1/2 inch beyond edge of plate. Flute edge.
For a baked pie shell, line pastry with double thickness of heavy-duty foil. Bake in a 425 degree F oven 10 minutes. Reduce oven to 375 degree F. Bake 20 minutes or until golden. Makes 3 single crusts.
To roll out the piecrust immediately, use a well-floured surface.