(1) A plumb bob is useful to check the alignment of the header with the sill.

(2) If the mass in question is a plumb bob, the horizontal component of F is important.

(3) The magnetic surveying instrument uses a magnetic compass card , plumb bob, and modified movie camera that is activated by a timer.

(4) If you have a good eyeball you can do it that way or use a plumb bob .

(5) The gyroscopic surveying instrument uses a gyroscope, compass card, plumb bob, and modified movie camera.