Described is a trowel having wings made from a pentagonal blank of stainless steel sheet that is typically 1.2 mm thick and bent about its central minor axis to include an angle theta of 105 degrees. The end of each wing has a peak at its outermost lateral extremity relative to the central axis. The part of the wing between the peaks and a working edge is bent toward the front of the trowel and, in use, is oriented toward the drywall panels. An elevated trailing edge of each wing has a narrow flange, respectively, which again points frontward and, in use, toward the panels. The flanges have radiused ends for smoothing the edges of the compound.