A slat is a narrow, flat piece of material (such as wood or metal) that is used as a support or to span an opening. In the context of a bed, slats are often placed horizontally across the side rails to provide support for the mattress and foundation instead of using a box spring.
A crosspiece is a piece of material that goes across or intersects another piece of material to provide strength and stability. In the case of a bed, a crosspiece is typically used to support the slats and prevent them from sagging or moving out of place.
Side rails in a bed are the long horizontal pieces that run parallel to the mattress and support the structure of the bed. They are usually made of wood or metal.
In a chair, horizontal crossbars are often used in the backrest to connect the vertical uprights. These crossbars help brace the uprights, keeping them stable and preventing them from wobbling. They also provide support for the back of the person sitting in the chair, making it more comfortable to lean against.
Both slats and crosspieces serve a similar purpose of providing support, stability, and strength in different furniture pieces like beds and chairs.
Crosspiece supported on side rails of bed to carry the spring. Horizontal crossbars in chairback to brace uprights and to support back of sitter.