How to Restrict All Users from Certain APs

I'm running Freeradius 1.0.1 using MySQL as the database backend. I need to configure the server so that all users are restricted from using certain access points (i.e. guest network). It appears I need to use a DEFAULT user definition in the users file, but I can't find any examples to work from. Has someone else done this? If so, I'd give anything to see how you did it. Thanks. Joe White System Administrator  @  Arvato Digital Services  @  108 Monticello Rd, Weaverville, NC 28787  @  828-423-0269