Screed has three meanings in building construction:a flat board or a purpose-made aluminium tool used to smooth and to "true" materials like concrete, stucco and plaster after they have been placed on a surface or to assist in flattening; a strip of plaster or wood applied to a surface to act as a guide for a screed tool ; the material itself which has been flattened with a screed. In the UK, screed has also come to describe a thin, top layer of material, poured in situ on top of the structural concrete or insulation, on top of which other finishing materials can be applied, or the structural material can be left bare to achieve a raw effect.