The sash weight was a lead cylinder hidden inside the wall next to the window. A rope ran from the window sash over a pulley at the top of the frame and down to the weight inside the wall. You lifted the window and the weight dropped and the weight held the window open. You pulled the window down and the weight went up. The sash weight was the window's counterbalance. Gravity working both directions at once.

The sash weight was invisible. You never saw it unless the rope broke and somebody opened the wall. Then you saw it. A lead cylinder the size of a rolling pin hanging inside the wall like a secret. The building had secrets in its walls. Lead weights on ropes doing work that nobody saw. The sash weight was the building's silent employee. It worked for a hundred years and nobody knew its name.

The rope broke. That was how you knew the sash weight existed. The rope was cotton and cotton rots and one day you lifted the window and the window would not stay up. It slammed down like a guillotine. A window with a broken sash rope was a window with an attitude. You propped it open with a stick or a book or a rolled-up newspaper and the prop was the admission that the building had outsmarted you. The building wanted the window closed and you wanted it open and the building won.

You replaced the rope. That was the repair. You pried off the trim and opened the access panel in the side of the frame and there was the weight hanging on its broken rope like a fish that got away. You tied a new rope to the weight and threaded it over the pulley and tied it to the sash and the window worked again. Ten minutes and a piece of cotton rope and the building forgave you for letting it break. The most satisfying repair in the apartment because you could see the mechanism and the mechanism made sense.

They replaced the sash weights with spring balances. A metal channel with a spring inside. No rope. No pulley. No lead weight in the wall. The spring balance works. The spring balance is efficient. The spring balance has no secrets. The sash weight understood that the best technology is the kind you do not see. The spring balance insists on being seen. The sash weight worked for a century in the dark and never complained. That is craftsmanship.

See also: Window Weight, Transom