This 90 degree angle corner chisel is used for squaring rounded corners.  Just place this self aligning chisel on a corner and hit lightly with a hammer, and lift the chip out with a chisel, for a perfect 90 degree square corner.  It will save many hours of work, and ensures a perfect fit.  It measures 2 and 3/4 in. long, with 3/8 in. cutter edge.  More efficient than a hand chisel and spring loaded.  Could also be used for a 90 degree pattern in lots of different materials.    $19.95