Tool tool, something we use to extend our power to act on the world, is as old as the first stone someone chipped to make a sharper edge. A tool is not only an object. It is an object plus the knowledge of how to use it and how to make it. When we pass that knowledge on, we pass on the tool in full. When we lose the knowledge, the object becomes a puzzle. Future people might find the stone and wonder what it was for. First, we have a need—to cut, to dig, to carry, to measure. Then we notice that something in the world can help: a sharp edge, a lever, a container. Then we shape it or choose it and learn to use it. We try. We fail. We try again. The knowledge of the tool lives in the trying. It is not only in the head. It is in the hands. So making and using tools is a way of knowing. We learn by doing. Tools can be misused. We might use the wrong tool for the job. We might forget how to maintain it. We might treat the tool as magic and forget the method. So when we pass tool-knowledge on, we pass on the method: how to test, how to repair, how to adapt when the material or the task changes. When continuity breaks, recovering tool-knowledge often starts with the simplest tools—and the willingness to observe, try, and correct. What is a tool you use? Could you teach someone else to make or use it?