Shavehorse Skill Tree
The shavehorse embodies the video game "skill tree", but for wood furniture making.
A shavehorse is essentially a bench with a lever attached. You sit on the bench, and push with your feet on one end of a lever. The other end of the lever then pinches against the bench, which lets you use it as a clamp to hold some wood, and frees up both of your hands to use other tools.
Figure 1: "Shaving horses in use" by Wikipedia user Hchristophersen.
The shavehorse works best with a drawknife, which is a long blade with a handle on each end. You pull a drawknife toward you with both hands to make a round or tapered piece from a rough-hewn stick or log. When sitting on a shavehorse and pulling a drawknife, you naturally push with your feet on the lever, which increases the clamping force on the workpiece.
In video games, especially role-playing games (RPGs), a common gameplay mechanism is that your character begins with a limited set of abilities. As you progress through the game, you attain more abilities by completing quests, defeating enemies, etc. Some of these abilities are hierarchical, forming a tree-like structure. In practice, this means you must acquire certain abilities before others.
For example, in Minecraft, a stone pickaxe is an upgraded version of a wooden pickaxe, so in the early stages of the game you would like to acquire a stone pickaxe quickly. However, your character starts with only their fists and no other tools. Before you can mine the stone ingredients for the stone pickaxe, you must first craft a wooden pickaxe. The wooden pickaxe in turn requires you to first build a crafting table. So the skill tree terminating in "stone pickaxe" might look like this:
Figure 2: Stone pickaxe skill tree in Minecraft
Shavehorse Skill Tree
Putting it all together, the shavehorse is an enabling technology that you can build with simple tools. After building one, you have a clamp which can be used for lots of work holding tasks. But also (and much like in video games) as soon as you have a shavehorse, it ironically becomes much easier to build more shavehorses!
Figure 3: Shavehorse skill tree
As you can see, crafting the shavehorse makes you more efficient at crafting tapered legs, which in turn improves your next shavehorse. Virtuous cycles such as this, where one improvement begets future improvements, make me feel like there is some inherent goodness in the design.