Building construction inside corner excluding water entry

An inside strip which is installed at the inside corner of a typical frame construction building having an external veneer. The framing defines a corner post with framing extending behind two walls at right angles. The two walls are covered with an external veneer such as a sheet layer or horizontal or vertical planking. At the inside corner to exclude the intrusion of water which might otherwise cause rotting, an inside strip is installed. It has the shape of a W-fold defining a center edge which is located at a position typically exposed along the inside corner. The elongate strip of W-fold construction includes outer marginal rectangular faces which are caught behind the wall during construction so that the strip is held in position to protect against the entry of water and inclement weather at the inside corner.