The shim was a thin wedge of wood or metal driven into a gap to make something level. The world was not level. The ground was not level. The floor was not level. The wall was not level. Nothing was level until someone made it level and the tool that made it level was the shim. A sliver of cedar or a folded piece of sheet metal pushed into the space between what was and what should be. The shim filled the difference.

You shimmed the door frame when the house settled and the door would not close. You shimmed the window when the sash rattled in the wind. You shimmed the toilet when it rocked on an uneven floor. You shimmed the formwork when the grade was off by a quarter inch. A quarter inch. The shim was the tool of the quarter inch. Nobody noticed a quarter inch until the concrete set crooked and then everybody noticed. The shim prevented the notice. The shim was invisible correction.

The carpenter carried shims in his apron. Cedar shingles split thin. He snapped them to width with his fingers and tapped them into place with a hammer. The tap was light. Too hard and the shim pushed the frame past level in the other direction. The shimmer of correction went both ways. Under-shimmed was crooked. Over-shimmed was crooked the other way. The skill was knowing when to stop tapping. The carpenter stopped tapping when his level showed the bubble centered. The bubble was the judge. The shim was the argument. The carpenter was the lawyer making the case for plumb.

The shim was the admission that perfection did not exist. Every shim said the same thing. This is not right and I am making it right with a scrap of wood thinner than my finger. The building was not ashamed of its shims. The building needed its shims. The shims were the building's way of negotiating with gravity and time and soil and weather. The building that had no shims was a building that had not been looked at carefully enough. Every building needed shims. Every life needed shims. The small invisible corrections that nobody saw but everybody depended on.

Nobody sells shims anymore except in plastic packages at the hardware store. The old carpenter made his own from scraps. The scrap pile was the shim supply. Every offcut was a potential shim. The carpenter never threw away a thin piece of wood because the thin piece of wood was the solution to a problem he had not encountered yet. The scrap pile was the future tense. The shim was the present tense. The level building was the result.

See also: Formwork, Spirit Level