This block and tackle overhead balance is constructed of a mill-finished steel U-frame housing. The internal working components include a spring, cord and pulley system. No end guides are required. Usually there is one balance located in the overhead for each operable sash. If your windows (sashes), are having problems staying up when opened, it may be that your sash balances or hardware needs to be replaced. The sash balances hold the weight of the window pane, over time, the springs can wear out or fail. Replace your sash balance for a smoother operation of your window and allow fresh air to enter your home with a window that stays open.