  Real world surfaces can often be modeled as a collection of edges, corners,
dents or spikes of varying roundness. These features exhibit individual
spontaneous wetting behaviors comprising pinned contact lines, rivulets or
cusps. If occurring in proximity to one another, as is often the case in
applications, these wetting properties interact, resulting in an overall
changed wetting pattern on the surface. Hence, there is considerable interest
in understanding when, and to what extent, interactions occur, and how wetting
then deviates from the wetting of isolated surface features. The present study
addresses these questions by experimentally and theoretically studying the
capillary interaction of sharp-edged 90{\deg} (outer) and 270{\deg} (inner)
corners in proximity to one another. It is shown that the spontaneous wetting
at the convex outer corner is in uenced by the concave inner corner even when
they are separated by a distance of several times the capillary length, while
the wetting of the inner corner takes place unaffected by the outer corner,
except when the separating distance is much smaller than the capillary length.
The final contact line shape at the inner corner is measured and theoretically
modelled for contact angles up to 90{\deg}.
