In a large bowl, mis margarine, shortening, and sugars with mixer until blended and creamy.
Stir in flour and salt.
(You can adjust the amount of flour- add most and then add little by little until point where the dough is not TOO crumbly or dry. If not, just add all at once. Use your hands to mix completely.) Roll dough out on lightly floured surface, about 1/8- 1/4 inch thickness, depending on how thin and crispy you want the cookies.
Cut with cookies cutters and place about 1 inch apart on ungreased cookies sheet (You can also roll dough into a 15 by 7 1/2 inch rectangle and cut into 1 1/2 inch squares).
Bake about 25 minutes or until set.
Cookies will not expand or brown much, so make sure you watch them so they don't get too browned- they will taste slightly burnt.