window is shown in fig1 b wherein the knife edge 18 if fig1 a and the associated obtuse angle vertex 20 on the window are replaced by a breakout point arrangement wherein the structure employs a blunt nose 22 mating with the breakout point 24 on the window the second embodiment relieves the dimensional constraints required in attempting to match the knife edge and vertex point to avoid aerodynamic irregularities in the assembled configuration damage due to chemical attack crazing scratching pitting or erosion of the exterior surface 26 of the window is repaired by grinding and polishing the exterior surface of the window to redeem the desired visual quality in the configuration of fig1 a the amount of material machined from the external surface 26 must also be removed from the mating surface 14 to retain the exterior mold line and avoid aerodynamic imperfections in the embodiment of fig1 b while machining of the mating surface 14 may be required in addition to machining of the exterior surface the dimensional requirements are significantly relaxed due to the ability to shim the mating surfaces to achieve the desired mold line tolerance a first embodiment of the present invention is shown in fig2 for refurbishment of a window with a damaged outer surface the surface.