A wood chair rail is a type of molding or trim that runs horizontally along the wall at about chair-height, typically around 32 to 36 inches from the floor. It serves both a decorative and functional purpose:

1. **Protection**: Chair rails were originally designed to protect walls from being damaged by the backs of chairs. They prevent scuff marks and dents that can occur from chairs being pushed back or moved.

2. **Decoration**: Today, chair rails are also used to add a decorative element to a room. They can break up large expanses of wall, create visual interest, and provide an opportunity to introduce contrasting colors or materials.

3. **Practical Use**: In addition to protecting walls from furniture, chair rails can also delineate spaces within a room. For instance, they can separate different types of wall treatments, such as paint and wallpaper, or distinguish between different areas of a room, such as a dining area and the rest of a living space.

Wood is a popular material for chair rails due to its durability, versatility in terms of finishes, and ability to complement various interior styles, from traditional to contemporary. It can be stained, painted, or left natural to match the overall decor scheme of the room.