A window roller is a type of roller that is used to facilitate the opening and closing of windows. Window rollers are typically attached to the sash (the part of the window that moves) and the frame of the window, allowing for smooth and easy movement of the window.
Window rollers can come in different shapes and sizes, depending on the type of window and the desired movement mechanism. Some common types of window rollers include:

1. Side-mounted rollers: These rollers are attached to the side of the sash and move along a track on the window frame.

2. Top-mounted rollers: These rollers are attached to the top of the sash and move along a track in the window frame.

3. Bottom-mounted rollers: These rollers are attached to the bottom of the sash and move along a track on the sill of the window frame.

Window rollers can be made from various materials, such as plastic or metal, depending on the application and environment. They can also have different levels of durability and resistance to wear and tear, depending on the frequency of use and the weight of the window.