A #backing #rod, also known as a #backer rod, is a flexible, cylindrical foam material 🏗️🧱 used in #construction joints and gaps to provide support 🛠️🔧 for #sealant or #caulk. A backer rod is typically made from open-cell or closed-cell #expandafoam, #polyurethane, or other compressible materials 🌐 https