In large bowl or crock, combine all ingredients, except roast and shortening, mixing well. Then add the rump roast, turning to coat. Cover and refrigerate about 36 hours; turn meat at least twice daily. Remove meat, wipe dry. Strain and reserve the marinade. In Dutch oven, brown meat in shortening, add strained marinade. Cover and cook slowly 2 hours or till tender. Remove meat. For each cup of gravy needed, combine 3/4 cup meat juices and 1/4 cup water; add 1/3 cup broken gingersnaps. Cook and stir till thick. Serves 10