In modern day sash windows, you're a lot more more likely to find a spring balance (or sash equilibrium) program. This can be a spring-loaded unit which counters the pressure of gravity, in result holding your sash window open up with no need for cords, pulleys and those metal counterweights.  https://fire-ratedsecondaryglazin10614.blogscribble.com/35658771/the-smart-trick-of-sash-windows-that-no-one-is-discussing