plumb line

"It's the lead weight from a plumb line."

Drop a plumb line from the top of the head down through the spine into the heels in first position, divide the body down this center, right from left.

“When I took down the remaining wallpaper in preparation for new wallpaper, I came across all her notes, measurements and marks for plumb lines. It brought back so many memories.”

The next day, they came back with a plumb line and a ruler to measure every distance between every component.

If a factory was nearby, he’d explain how you used a plumb line to get the chimney straight and why the windows had been placed a certain way to let in the maximum light.