Wallboard's trade quality Ply Mitre Box makes cutting 45 and 135 degree angles in most standard size cornice simplep 
Made from construction grade plywood n Dual cutting at 45º & 135º
Sides and base are both 20mm thick and glued together for added strength
Steps in base accomodates 55mm, 75mm, 90mm & 100mm cornice
Cuts are not full depth to maintain strength while box is in transit