If you don't what know the term "plumb" means, you may be surprised to hear that it doesn't directly have anything to do with plumbing. It's actually used to describe when a edge or surface is perpendicular to to a level line, with true vertical orientation. (Think when you're framing a house or installing a door jamb.) To know if a surface is plumb, you can use a level, which usually has at least one vial to read plumb, or a plumb bob, which is a weight suspended by a string....
Terms of the Trade: What Does "Plumb" Mean?
Terms of the Trade: What Does "Plumb" Mean?
