In a bowl, combine cheddar and Parmesan cheeses, butter and water until well mixed. Combine flour and salt; add to cheese mixture. Stir in oats and sunflower kernels. Knead dough until it holds together. Shape into a 12-in. roll. , Cover; chill for 4 hours or overnight. Allow to stand at room temperature for 10 minutes before cutting into 1/8-in. slices. Preheat oven to 400°. , Place on greased foil-lined baking sheets. Bake until edges are golden, 8 to 10 minutes. Slide crackers and foil off baking sheets to wire racks to cool.