These are fragments of anti-boarding netting, recovered from the Mary Rose.
Made of hemp and fixed with flat seizings, anti-boarding netting would have covered the upper decks of the ship, possibly fixed in place permanently, to prevent the ship being boarded during a battle. In the time it would take an enemy soldier to cut through the net, he'd have been open to attack from the crew below, and would be lucky to survive long enough to board properly,
Sadly, its efficiency at keeping people out was matched by its efficiency at keeping people in. When the Mary Rose sank on 19th July 1545, the majority of the crew would have been underneath this netting, which may account for why, out of a crew of over 500 men, only 30-40 managed to escape.
Image © The Mary Rose Trust