In a large bowl, cream shortening and sugar until light and fluffy. Beat in molasses and egg. Combine the flour, baking soda, ginger, cinnamon and salt; gradually add to the creamed mixture alternately with water mixing well after each addition.
Pour into a greased 13x9-in. baking pan. Bake at 400° for 13-15 minutes or until a toothpick inserted in the center comes out clean. Cool completely on a wire rack.
In a small bowl, combine the confectioners' sugar, vanilla and enough milk to achieve desired consistency. Spread over cooled bars.