{HEAD ~ The welding seam} can have any desired shape, as long as it exhibits a sufficient length and strength, in order to ensure a permanent joining of {TAIL ~ the sheets} 
{ HEAD ~ The welding seam } can have any desired shape , as long as it exhibits a sufficient length and strength , in order to ensure a permanent joining of { TAIL ~ the sheets }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL