Mix together shortening & sugar, until smooth & creamy. Add baking soda, salt and eggs; mix well.
Combine cream of tarter and flour. Add flour mixture a little at a time; after 4 C add sour milk. Continue to add flour until well blended. Mixture will be thick.
Refrigerate over night. Roll out with flour & rolling pin; cut with cookie cutters. Makes a lot of cookies. Can freeze left over dough.