Illustration of the attribution of a flag F to a given star from the Xiang et al. (2017) list. Shown are images of the dust distribution in vertical planes containing the Sun and the star. The dark areas correspond to high dust opacity. The LOS to the target (green marker) is shown as a green dotted line. HD 143567 (top) is attributed a flag F=1 since most of the extinction is generated in a single very dense nearby cloud. The more distant HD 192216 (bottom) is attributed a flag F=0 since at least two dense clouds separated by a large distance contribute to the extinction.