actually a bridge used to build upon what students already know to arrive at something they do not know. If scaffolding is properly administered, it will act as an enabler, not as a disabler" (Benson, 1997, p. 126). According to Greenfield (1999), The scaffold, as it is known in building construction, has five characteristics: it provides a support; it functions as a tool; it extends the range of the worker; it allows a worker to accomplish a task not otherwise possible; and it is used to selectively aid the worker where needed. (p. 118) Dixon, Carnine, and Kameenui (1993) remind us that effective scaffolds must be "gradually dismantled" in order to remain effective (p. 100). However, if scaffolds are dismantled too quickly, learning does not occur and the learner becomes frustrated in the process. You probably have noticed that we use the term scaffold as a noun rather than a verb, because a present-tense verb may imply a process that is ongoing, which places teachers and students at risk of dependency rather than independence. Guidelines for Instructional Scaffolds Over the decades that the field has been working to clarify instructional scaffolds, a number of general guidelines have been developed. In 1983, Applebee and Langer identified five features necessary to scaffold students' understanding. As you consider each of these, notice how much they have in common with differentiated instruction and Understanding by Design (Tomlinson & McTighe, 2006): . Intentionality: The task has a clear overall purpose driving any separate activity that may contribute to the whole. . Appropriateness: Instructional tasks pose problems that can be solved with help but which students could not successfully complete on their own. . Structure: Modeling and questioning activities are structured around a model of appropriate approaches to the task and lead to a natural sequence of thought and language. . Collaboration: The teacher's response to student work recasts and expands upon the students' efforts without rejecting what they have accomplished on their own. The teacher's primary role is collaborative rather than evaluative.