A louver slot is employed upstream of an array full coverage film cooling holes where cooling air is supplied using a combination arrangement, with cross-flow and impingement together. The louver consists of a row of film cooling holes, contained within a specially-designed device which concentrates, and directs the coolant from a slot, so that it then advects as a layer downstream along the test surface. This louver-supplied coolant is then supplemented by coolant which emerges from different rows of downstream film cooling holes. The same coolant supply passage is employed for the louver row of holes, as well as for the film cooling holes, such that different louver and film cooling mass flow rates are set by different hole diameters for the two different types of cooling holes. Full-coverage blowing ratios are constant with streamwise location along the test surface, and range from 3.68 to 5.70. Corresponding louver slot blowing ratios then range from 1.72 to 2.65. Heat transfer coefficient and adiabatic effectiveness distributions show less variation with streamwise development, relative to results obtained without a louver. When compared at the same effective blowing ratio, spanwise-averaged heat transfer coefficients are consistently lower, especially for the downstream regions of the test plate, when the louver is utilized. With the same type of comparisons, the presence of the louver slot results in significantly higher values of adiabatic film cooling effectiveness (spanwise-averaged), particularly at and near the upstream portions of the test plate.