Wood filler is a suspension of a sandable material in a solution of hardening resin that has the ability to soak into wood fibers and bond with them. An example the ancients may have used ??? and one still used by woodworkers today ??? is a mixture of wood dust (cellulose) and lacquer, varnish or glue. Some contemporary products, such as DAP???s Plastic Wood All Purpose Wood Filler, combine wood fibers with a solvent-based hardening resin while others combine gypsum, limestone or attapulgite (a fibrous clay mineral) in a solvent- or water-based hardening resin.