Knife
The Tinkers' knife is used for mid-game resource gathering. This has a much greater yield than the crude knife.
As a crafting tool, the knife can be used to convert several items (see recipes below). This doesn't consume the knife, just causes some durability loss. Additionally, if you have Tinkers' Tool Leveling installed, the tool will also gain experience and the attribute Crafty!
Flint Shards
Sticks
String
Tools
Crude Knife
Crude Hatchet
Crude Saw
Tinkers' Knife
Tinkers' Saw
Mod Integrations
Tough As Nails
Constructs' Armory
Health
Crude Bandages
Bandages
Configuration
Client Configuration
Common Configuration
Server Configuration