A novel longitudinally corrugated paper-layer in continuous production has been generated out of an innovative technology for imparting customized stretch to fibrous webs. Traditional corrugated board consists in a transversally corrugated layer (fluting) which is glued to at least one second layer (liner) for holding the corrugations in place. The novel longitudinally corrugated layer is produced as a stable wave structure without the need of gluing on a second sheet. For additional stiffness in MD and in CD in a final panel, said layer can be combined to any traditionally produced corrugated material. The technology on which this novel longitudinally corrugated paper-layer is based, can also impart separately both CD and MD stretch to paper for the generation of 3D-deformed patterns in order to e.g. stiffen the corrugated board with appropriate structures, or to create layers with 3D-impressions for communication or aesthetic purposes.