SASH WINDOWS
 
Description:
A sash window or conservation box sash window has two parts (sashes) that overlap slightly and slide up and down inside the frame. The two parts are not necessarily the same size.
    
Operation:
Lead Weight Mechanism (Timber sash window)
weight mechanism using weights on cords ideally balancing  your window to stay in position you left it Spring mechanism (PVC or Timber sash window)
Using strings  allows you to add tilting option which is very helpful for cleaning and ventilation