3Determine whether the joists in your ceiling run parallel to the screen or toward the screen, as shown below. Use a stud finder if necessary.
4Locate two adjacent joists on opposite sides of the location where you plan to install the mount. Mark the exact center of one joist, to indicate where you will attach the ceiling plate. Then measure 16.25 inches to the second joist and mark it as shown.
Warning
Use a stud finder to locate the center of the first joist. You must find its exact center to attach the plate securely.
Tip
With a second person’s help, you can mark the second joist by holding the plate against the ceiling. Carefully align the plate with the mark that indicates the center of the first joist, then mark the second joist at the location shown.
Mark center of joist
Joists run toward screen:
Ceiling joist
Screen
Ceiling plate
Joists run parallel to screen:
Mark center of joist 
Screen
Mark a point 16.25 inches from the other joist
Mark a point 16.25 inches from the other joist
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