Abstract: The siding for a building exterior may be double-sided, the siding being in the form of tongue and groove boards having a rough cut surface finish on one face and a log-profile on the other face. A corner block structure simulating traditional dovetail log joints may be used with the log-look face and provides a low cost, easily fabricated corner block particularly suited for ready installation to the exterior corners of a building, in finishing and protective relation therewith.