I learned to install a door one day in small-town Arkansas, on a nondescript tract home with pinkish, mottled brick that was dated even before the mason finished his work. The door was delivered from the lumberyard as a unit, already hinged and hung in its jamb, and my boss, Dave, gave me all the information I needed to install it. He told me how to make sure the studs on the hinge side of the opening were plumb in two directions, and how to tack up shims to correct for the framers’ hurry. He explained that a push on a corner in one direction would effect a logical movement in another. All I had to do was fill the framed opening with the door, making all things plumb and flush.