To get a larger open area we have developed on the basis of our fine perforation slotted hole sheets. The length of the slotted hole always runs parallel to production width. To increase length and width as given on page 12 and 13 the sheets can be joined together by roll resistance welding. Sheets with an initial thickness of 1.0 mm upwards can also be butt-welded dependent on pitch of holes. Manufacturing tolerances for openings and other dimensions are dependent on manufacturing process and ingoing material.