Kill spiders
Kill cave spiders
Break cobwebs with a sword
Use a fishing rod
Trade with a wandering trader
Find string in dungeon chests
Find string in desert temple chests
Find string in jungle temple chests
Find string in abandoned mineshaft chests
Find string in bastion remnant chests
Find string in desert village chests
Find string in ruined portal chests
Find string in shipwreck chests
Find string in woodland mansion chests
Find string in ancient city chests
Find string in trial chamber chests
Craft wool into string is not possible