We propose an improved hole array to enhance the cooling performance of a perforated blockage. The internal passage in the trailing region of the blade was modeled as a wide square channel with three parallel blockages. Various configurations of perforated blockages were tested with a fixed Reynolds number. The baseline design had holes positioned along the centerline of the blockage in the lateral direction, and the array pattern, hole size, and hole direction were manipulated to enhance the cooling performance. Experiments were performed to obtain information on heat transfer and pressure loss. A naphthalene sublimation method was adopted to obtain detailed heat transfer distributions on the surfaces, using the correlation between heat and mass transfer. The pressure was measured at several points to evaluate the pressure loss. The proposed inclined hole array showed noticeably improved cooling performance, as much as 50% higher than the conventional configuration.