if the side of the cabinet is not exposed, then the only visible area of the cabinet is the door. However, if the side of the cabinet is exposed, then the color of the carcass - white - is visible, and this may clash with the rest of the cabinets. In those cases, you would need replacement gables - sides that are of the same color as the cabinet door - so that the front and side of the cabinets do not clash. For each type of exposed end, you would need a different type of replacement gable. The most common is left base and right base, for regular base cabinets. There is also corner base - for a corner base (also right and left), diagonal corner - for diagonal wall cabinets that weren't being put in a corner, rather as a peninsula coming off the wall. The DC is used for the exposed sides. Regular replacement gables usually work 90% of the time.