Place your knife at the side of the tile at the bottom of the cut you just made halfway through the tile.
Best way to cut drop ceiling tiles with a reveal.
Pull the knife down along the side to remove the edge of the tile and create a shadow line.
Pull the straight edge back about 1 2 inch and cut the vertical portion of the tile reveal.
Measure the location of holes required in the tiles such as those for lighting or air vents.
Transfer those measurements to a ceiling tile and draw an outline of the cut on the front of the tile.
With the tile cut to width i then make the shoulder or horizontal cut for the ceiling tile reveal.