Things You'll Need
Chalk snap line
Whether you are laying out new lighting fixture locations, establishing a starting point guideline for an acoustic installation or simply needing a precise measurement of the ceiling surface, you need to define a straight line across your ceiling. This rudimentary procedure is easy to complete and can be adapted to any need for an accurate measurement or to mark a straight line for any ceiling project.
Access the ceiling surface from a stepladder at either end of the point where you wish to establish the ceiling line or measurement.
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Measure from the nearest perpendicular room wall as a reference and mark the desired point for the ceiling line on the ceiling's surface.
Move to the opposite wall and repeat Step 2 to mark the other end of the ceiling line on the ceiling's surface.
Position a helper at the opposite end of the ceiling to access the first marked end of the ceiling line to hold the end of a measuring tape or chalk snap line on the mark.
Pull the tape measure so that it is held as tight as possible against the ceiling surface and read the dimension of the straight line measurement of the ceiling. To mark a line, hold the chalk line taught between the two end marks and snap a line by pulling slightly downward on the chalk line and releasing it to mark the line.
Typically, for a square or rectangular room, a correct, straight measurement of the ceiling can be determined at the top line of any perimeter wall.
The successful marking of a straight, clean chalk line depends on the line being held securely and pulled tight to snap the line. Although you can use a nail to hold the end of the line for the marking, it is recommended you enlist a helper in holding the chalk line in place when completing this procedure.