caulk

a filler used in construction and repairs to make joints watertight

Caulk is a flexible material used to fill gaps, joints, or cracks in different surfaces, like walls, windows, or pipes. It helps to prevent air, water, dust, or insects from entering through these spaces. Caulk can be made from various materials, including silicone, acrylic, or polyurethane, and it is typically applied with a caulking gun. Once applied, it dries to form a durable, smooth seal that improves insulation, prevents leaks, and enhances the overall appearance of the area.