Wood Fillers and sealers are applied on the bare wood surface. This application is done much before the clear wood finish is applied finally. A filler is a transparent paste applied on the wood to fill any minor dents or grain pores. A sealer is a layer laid on top of the filler. The sealer fills the minor pores on the bare wood. A sealer effectively smoothes and evens out the surface. A sealer coat is essentially a barrier coat between bare wood and topcoats. In the absence of a sealer coat, the appearance of the final topcoat will not be aesthetic as the performance of the topcoat has been compromised.