Not many people know why the white braided rope used in so may theatrical and rigging applications is called sash cord.
Back in the days of wooden double hung windows (lots of older houses still have them), raising and holding the bottom part of the window(called a “sash”) open was accomplished by a counterweight that was hidden in the window frame, behind the wall.
As you raised or lowered the window, that weight counterbalanced the weight of the window frame and the glass. The counterweight made it easier to lift the window sash and held it open until you were ready to close it.
A properly counterbalanced window could be easily raised with just one hand and the lowered with almost no effort.