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The alignment requirements of the aperture-mask color kinescope, combined with the necessity of maintaining the alignment of aperture mask and glass phosphor plate during the operation of sealing the viewing-screen assembly within the tube, have resulted in the development of new assembly methods and techniques. The aperture mask of copper-nickel alloy is stretched tightly on one side of the spacer frame and the phosphor-dot plate is loosely clamped on the opposite side; alignment of the two parts is maintained by a fixed pin at one end of the frame and a sliding pin at the other. The two-piece metal-shell construction permits insertion of alignment fixtures for glass-neck and electron-gun sealing prior to the installation of the screen assembly. A reference plane is provided for these operations by screen-assembly mounting posts inside the shell. An internal high-permeability magnetic shield is also fastened to these posts. The final envelope seal is made by welding together the flanges on the two shell sections by means of an inert-gas arc. These flanges help to protect the tube faceplate and viewing-screen assembly from mechanical and thermal damage during the welding operation.