plumb line
perpendicular

The supporting leg is seen behind an arm on the same side that hangs down like, in effect, a plumb line.

You could have used his spine to draw a plumb line.

From the outside corner of the joint where the top plates meet on the ceiling drop a plumb line to the floor.

Next I checked the depth of the hole, using a board and a plumb line.

Straight as a plumb line she sat down opposite his desk.

She tried setting up long plumb lines and dropping things, with inconclusive results.

You could have dropped a plumb line from the small of her back to the floor.

It involved the use of a bar with a plumb line, attached to a wooden handle.

The part that is cut off should then be hung in sequence with a plumb line.

It even gave instructions on how to obtain measurements using the plumb line.