Place chunks of shortening in bottom of food processor bowl. Add flour and salt. Process with 5 or 6 quick on off turns or until mixture resembles course oatmeal. Combine water and vinegar. With processor running, add liquid in steady stream just until dough begins to gather around baldes, about 10 to 12 seconds. Immediately remove dough, press into a ball, divide into 2 and wrap each piece separately with plastic wrap, shaping each piece into a disk. Refrigerate 1 hour. (At this point, dough may be frozen for future use.) After allowing to warm up a bit, roll out on floured board to about 1/8 thick and fit into pie or tart tin. If baking a crust to be filled later, freeze for 15 or 20 minutes before baking to minimize shrinkage. Prick bottom all over with fork. Fill with foil and pie weights. Bake at 400 F for 10 minutes. Remove foil and weights and bake 5 to 7 minutes longer until golden. Yields 2 9 pie crusts.