I have several plunge routers. I leave them set up for different operations. One of them is a PC 690 that came with a fixed base and a plunge base. I can’t figure out why I want a fixed base in addition to the plunge base. It's been sitting on a top shelf gathering dust for a few years. Seems to me my plunge base will do everything the fixed base will do...... plus plunge. What am I missing???