Bear HidePick it up to discover it.
Vile RibcagePick it up to discover it.
Black MetalPick it up to discover it.
Linen ThreadPick it up to discover it.
ForgeDiscover and use at level 4 or higher.
Discovery is separate from having enough materials to craft. Check shelter, fire, placement, and station access in-game. This checklist cannot diagnose broken mods or save files. Each alternative recipe is listed separately.