This is the basic way to unlock all equipment types. Continue crafting an item type until that item is unlocked. For example, the Knife will unlock Swords and Axes. The first Sword, the Shortsword, comes from crafting the Knife. The first Axe, the Hand Axe, comes from crafting the Dagger.
Blueprints are also given for free when Workers are hired if a blueprint has not already been unlocked. If 2 or more sources would unlock the same blueprint, nothing happens when the second (or further) instance would occur. For example, hiring the Druid will unlock the first Remedy, the Healing Herb. The Healing Herb is also unlocked by the Crow Stick. If you would unlock Healing Herb by crafting Crow Sticks, and already have Healing Herbs unlocked, instead nothing happens at that level of progress. You also do not get a replacement blueprint if you already unlocked the Healing Herb when you hire the Druid.