Woo filler, also known as Wood putty or Plastic wood, is a substance used to fill imperfections, nail holes or pores in wood prior to finishing. "Wood putty" or "plastic wood" usually refer to the thicker version used to fix imperfections and small holes, while "Wood filler" refers to the thinner version used to fill pores. It is often composed of wood dust combined with a binder that dries and a diluent, and, sometimes, pigment. Pore fillers used for large flat surfaces such as floors or table tops generally contain silica instead of or in addition to wood dust. Pores can also be filled using multiple coats of the final finish rather than a pore filler.