When using a router you can also use it with jigs. Jigs are a thing that a tool, like can attach to or be used on a tool to use it in a way that is not originally intended. Such as if you use a a flush trim bit you can use, you can have a template, another piece of wood that goes behind it it will then have an overhang the flush trim bit runs over your template cutting your your other piece of wood the same profile. A more complicated, jig could be this one right here. This jig is used to add a radius to this piece of mahogany. First the piece of mahogany is cut cut close to a curve but not all the way to it. Piece is inserted into the jig, plunge router is placed on the jig and then is able to take passes over the wood while being able to slide the full length. To give you an idea of how complicated a router jig can be I am going to show you this one here which creates a dome out of a solid block of wood. A plunge router mounts to the top of it, and is able to slide the full radius of the block. At the same time, the base rotates, each time you make a pass, you rotate the block a small amount until you go the full three-hundred and sixty degrees of the dome.