A typical “Window” unit comprises two components. The operable part that holds the glass is called a “sash”. The “sash” is put together using 4 wood components, Stiles, the two vertical parts that travel the height of the sash on either side and Rails, “Top” rail and “Bottom” rail, go between the stiles at the top and bottom respectively. These components are profiled on one edge (inside) and glass is held by these profiled edges. These profiled edges are commonly referred to as “sticking” detail. In most cases similarly profiled pieces are then installed on the non-profiled side (outside) to hold the glass. These pieces are called “stops”.
Commonly used profiles (sticking details)are

  • Ogee – an ‘S’ shaped profile
  • Ovalo – a quarter arch profile
  • Square – Flat or stepped.

The sash(s) in a window are divided by glass panes. It can also have an undivided one piece of glass. The wooden pieces that divide the sash and glass portion between the Stiles and the Rails are termed as “Muttin Bars”. These bars are also profiled on both sides to match the Stiles and the Rails. The bars hold the glass.

TDL – When the bars divide the inside space of the door into small sections for small panes of glass then this configuration is called True Divided Lite or TDL.


SDL – For increased efficiency of insulated glass the sash is made with one piece of glass but wooden stops with profiles are installed on either side of this glass to “simulate” the look of divided panes. This configuration is termed Simulated Divided Lite or SDL.


The second component of the window is the frame that holds the sash and slides onto the opening in the wall. Based on the type of window a window could have a single or multiple sash.