Casement windows or Openable windows are simple in design. Casement window, earliest form of movable window, wood or metal framed, with hinges or pivots at the upright side of the vertically hung sash, so that it opens outward or inward along its entire length in the manner of a door. They are mostly used in residential applications.

Unlike Sliding Windows, they are hinged on the side, with the sash opening horizontally either to the left or to the right. Some windows have additional panels for fixing mosquito mesh, grils, etc. these windows can also be made out of hollow shapes which have grooves for weather strips. Extruded glazing clips are used for fixing glass. This eliminates ugly display of screws. This allows for full ventilation from top to bottom of the window opening and the extended sash can catch the breeze and direct it into the house for better air flow.

A Casement Window (or Casement) is a window that is attached to its frame by one or more hinges. Casement windows are hinged at the side (Windows hinged at the top are referred to as Awning windows. Ones hinged at the bottom are called Hoppers). They are used singly or in pairs within a common frame, in which case they are hinged on the outside. Casement windows are often held open using a casement/friction stay.

Casement Windows usually contains glass, although option for fly mesh (mosquito net) is also available. The same section can also contain fly mesh and are usually applied along with glass to solve the problem of mosquitoes. These sections are usually applied on Rectangular Tube (RT) to provide better stability and aesthetics.