In the construction of buildings, scaffolding is used to support structures until they are strong enough to stand on their own. This idea is intended to apply similarly in education, where scaffolding instruction means supporting students until they can independently and successfully perform a specific task. In the construction metaphor, scaffolding is removed once the building is done. In learning, similarly, scaffolding is systematically reduced as students demonstrate increasing competency. A common misunderstanding of scaffolding is that prerequisite knowledge, skills, or cognitive stages exist that students must obtain before they can learn new material. Rather than basing scaffolding on purported sequences of knowledge or developmental stages, it should be adjusted based on student performance. Scaffolding is necessary in cases where failure could be dangerous or unproductive—i.e., when it poses risks to life or property, when the result is demotivating, or when it is unlikely to be a productive experience.