Abstract: Disclosed is a color bar mask for adjusting television receivers of the type used in closed circuit systems. The mask comprises a plurality of vertical colored translucent bars spaced between opaque bars. The bars are dimensioned so as to match up with color bar signals generated upon the screen of the receiver. The mask is designed to leave a substantial part of the screen exposed so that the bar signals generated on the screen can be compared with the same bars as viewed through the translucent color bar pattern. The mask is secured to a frame. The frame is pivotally secured to a rectangular member which rests on the receiver so that the mask may be conveniently disposed and removed from the screen.