The invention relates to multi-spot-welding machines for the production of lattice gratings suitable for use for example as walk ways, and which consist of upright flat bars parallel to one another and cross-bars welded transversely into these and again parallel to one another. The flat bars are usually fed intermittently to welding electrodes. The machine of the invention has at least one pair of cooperating electrodes which are aligned in the feed direction of the flat bars and spaced apart a distance substantially equal to the desired spacing of the cross-bars. The or each pair of electrodes is pressed in turn against each pair or cross-bars to be welded and the upright flat bars themselves act as current bridges between the electrodes of the or each pair. An abutment supports the flat bars against the force of the welding electrodes and this abutment has considerably greater hardness and wear resistance than the flat bar material. The abutment is of suitable design and is suitably positioned to correct the deformation of the longitudinal bars which occurs when the transverse members are welded thereon.