Many styles and shapes of router plates are available. Many routers and router plates allow you to adjust the height of the router bit from above the router without having to remove it for adjustment. Today, a router table is almost a must if you use any of the large-profile bits available; some bits require you to use a table only. Following a few simple steps will make the installation an easy task.
Place the router plate on the table. If the router will be used primarily for large panel work, place the router plate toward the back of the table. This will allow a large work surface to support the panels. If you'll primarily use the router table for small parts, place the plate toward the front. This option keeps the work close to you while router. Otherwise, place the router in the middle of the router table for a combination of router needs.
Cut some 3-inch strips of MDF to use as a template for the router plate. Use a table saw. You need a straight-edge for the template, so do not cut freehand; use a fence to ensure a straight cut.
Place two pieces of the MDF strips along the long side of the router plate. Use double-sided tape to hold them in place.
Take the router plate out from inside the MDF strips, The MDF now acts as a pattern for the plate.
Router out a 1/2-inch track around the inside of your pattern. This will be cut to the depth of your router plate plus 1/8 inch. This step allows the router plate to be recessed into the table so it can be adjusted to be flush with the router tabletop.
Remove the MDF template from the tabletop. Drill a 1/2-inch hole inside the track that you just routed.
Saw out the inside of the track with a jigsaw. Use the inside line of the track as your cutting line reference. This will allow the router to fit through the tabletop.
Install the router and router plate; refer to the directions for how to level the plate.