05. Measure and mark
measure 48 inches
From the lowest point in the ceiling measure down 48 inches. Make a mark with your pencil.
Check for the lowest point in the ceiling by using your level or one of the panels and see if the ceiling dips at any point.
Draw level line
Place your level horizontally under the mark you just made at 48 inches. Once level, draw a straight line along the length of your level.
Make sure this line is clear and level. Not to put on too much pressure, but this line determines how level your entire project will be...