A brief tutorial for the subclassing part of the FreeBSD configuration system (known for years as newbus). The author will present work bringing this power to legacy portions of the system, as well as suggestions for future work in this fruitful area. This lecture will present a background of the FreeBSD driver system. The subclassing part of this system is radically under-documented. A companion document for this lecture will amplify the current documentation and provide additional examples to illustrate the power of the subclassing system. The lecture will then shift to reviewing the work the author has done to use these techniques to help map items in the kernel device tree to device nodes in the devfs tree.