A video that shows you how to cut a external mitre (for a corner that projects into a room) without using a mitre box:

  • Make sure you know which edge of the plaster coving is the ceiling edge, and which edge is the wall edge
  • An external mitre means that you need to 'add on' to the top edge
  • Make sure you make the 'wall mark' and then square it up along the bottom edge
  • Add the top edge mark of the cornice using the projection measurement
  • The cut in the plaster coving will go from the bottom edge to the top edge
  • Enlist the help of a spare pair of hands to hold the coving at the correct projection depth
  • Cut using a saw to achieve the correct 45 degree mitre
  • Repeat the process for the other end of the coving.