Pattern help

Need some clarification. I am knitting a shawl with a lace edging. Just finished the main body. The pattern calls for a lengthwise edging. While the pattern instructs to leave all stitches on the needles, it says to block the piece before adding the lace edging. How do i block a piece that is still on the needles??? The piece is on circular needles but stretched out it is longer than the needles!? Help!

Put the sts on some sort of thread to block it. Crochet thread works well, sometimes plain dental floss will work.