A modular welding table where the work surface is made up of a plurality of plates that can be easily slid to and fro, adapting to objects of different shapes is disclosed. The cover member when in the first position is movable to the second position by a force exerted thereagainst by a flow of at least air discharged from the duct. The holder is formed as an open frame defined by a top plate, a parallel bottom plate and a pair or more side plates extending between the top plate and the bottom plate. When the unit is not fastening by the screw, the screw is elastically supported via the wire piece on the fixing member and the elasticity is given by a portion of the wire between a portion fixed by the fixing member and the bent portion.