Silk threads made by your Villagers:
Luxury sheets are a sign of how far your refugees have come!
Your villagers have discovered a way to turn Spider String into quality Silk fibers for fine sheets and bedding. Silk can only be obtained from your Villagers in Community Chests in the Storeroom.
Silk on en.wikipedia.org
Nylon Silk Bed (Advanced)
Village Beds Main Page