it might be plasterboard joint tape, but im not 100% sure
like this: http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9273282&fh_location=%2f%2fcatalog01%2fen_GB&fh_search=joint+tape&fh_eds=%c3%9f&fh_refview=search&ts=1198156146915&isSearch=true