Abstract: The present invention provides an apparatus used with materials fabrication power tools to reduce errors associated with loose-fitting materials fabrication guides. The present invention provides a materials fabrication surface having a slot and a guide variably positionable within the slot and capable of mounting a fixture such as a miter gauge. The guide includes an expandable member coupled to the guide member such that, upon expanding, the distance between the guide and the walls of the slot can be reduced. By reducing the distance between the guide member and the slot walls, inaccuracies associated with the guide member-to-slot interface are eliminated. In this manner, a fixture, such as a miter gauge, can be mounted and used on the guide and used with the power tool to increase accuracy and repeatability associated with the materials fabrication operations.