Outside Corner Angles

• 1). Measure from the corner back along one side, to the end of the wall. Transfer the measurement to a piece of trim that's longer than the wall. Put the marks on the top edge of the trim.
  
  
• 2). Stand the trim on the miter saw the way it will go on the wall. Position the marked line for the outside corner under the blade. Turn the blade to 45 degrees, pointing away from the measured span. Make the cut.
  
  
• 3). Repeat the process for the trim coming off the other side of the corner, with the trim sitting on the opposite side of the blade and the blade swiveled to 45 degrees in the opposite direction as before (so it's still pointing away from the measured span).
  
  
• 4). Cut the opposite ends of both pieces as needed, according to where they go to an outside corner, inside corner or butt against a wall.
  
  
• 5). Hold the two pieces to the corner, with the mitered cuts meeting at the edge of the corner and forming a square angle. Secure the pieces with the trim nailer, shooting nails at the top and bottom edges, about every foot.
  
  

Inside Corner Angles

• 1). Measure from the inside corner outward in one direction. Transfer the measurement to a piece of trim. Cut the trim straight across at the mark, with the miter saw blade set at 90 degrees. Cut the other end as needed.
  
  
• 2). Secure the piece with a trim nailer. Position it so the straight-cut side butts up against the adjacent wall of the inside corner.
  
  
• 3). Measure out from the other side of the corner and transfer the measurement to a piece of trim. Set the trim on the miter saw as it will go on the wall. Turn the blade to 45 degrees, pointing inward, toward the measured span. Make the cut.
  
  
• 4). Cut around edge of the miter where the exposed wood meets the trim face using the coping saw. Position the coping blade so it's slightly back-cutting as you follow the contours of the miter. The finished cut should look like a hook that follows the contours of the trim.
  
  
• 5). Set the coped piece on the wall, with the cut side sitting against the previously installed trim. The edge of the second piece will fit over the face the first piece. Secure the second piece with the trim nailer.