These devices, typically made of rubber, foam, metal, or plastic, are attached to door frames to close gaps and prevent the passage of air, water, insects, and dust. A common example is the strip of rubber found along the bottom of an exterior door.
Effective gap sealing contributes significantly to energy efficiency by reducing drafts and heat transfer. This leads to lower energy bills and a smaller carbon footprint. Furthermore, these barriers enhance indoor comfort by stabilizing temperatures and reducing noise infiltration. Historically, simple methods like stuffing rags into cracks were used. Modern materials and designs provide substantially improved performance and durability.