sash cord 
noun
A strong cord attaching either of the sash weights of a sash window to a sash: [mass noun]: they trussed them in sash cord...
- When replacing sash cord, put a 16d nail into the end of the cord before feeding it through the pulley.
- Also, if your sash cords dangle near the floor, install a hook to hang them higher up - they're a strangulation risk.
- Be sure you do not cover the pulleys and that the sash cords or chains can run free.