Adhesives and glues are liquid substances that attach materials and prevent them from separating after drying. These fasteners often replace or reinforce mechanical fasteners. Only load-bearing structural adhesives can form load-bearing bonds. Adhesives in construction materials hold together permanently, but do not carry loads. Spray adhesives are useful when bonding large surfaces. Both surfaces must be coated with contact adhesive. Superglue is one of the fastest curing and bonding adhesives. For connecting and sealing light-to-medium-weight materials, hot-melt adhesive sticks are used. There are wood glues that bond wooden parts together, or other wood-specific materials.