Pocket hole joinery is one of the best methods for joining two pieces of wood to ever come down the pike. But the pocket holes by themselves aren't all that attractive. In the majority of cases, it doesn't matter - the holes are hidden from view on the back surface of a face frame, under a tabletop, or on the back of a picture frame. But what do you do about pocket holes that will be visible on a finished project? The answer: pocket hole plugs.
Pocket hole plugs can be used in a couple of ways: Using a plug of the same species as the wood you're filling is a great way to hide pocket holes. With a little careful grain matching, you can make the hole all but disappear. Or, you can show off the oval shape of the pocket hole by using a plug cut from a species that contrasts in color with your project.
When you use pocket hole plugs, remember that they aren't designed to sit perfectly flush with the surface of the hole when you glue them in. The plugs are made to take variations in pocket hole depth into account. The amount of plug left sticking up above the surface of the wood will vary depending on the thickness of the material you're plugging, and on the depth of hole your jig is set to make. It's normal for them to sit a good bit proud of holes on the shallow end of the range.
To take off the excess plug, our friends at Kreg recommend using a flush trim saw for just a few plugs, and a laminate trimmer outfitted with a bullnose bit if you have a lot of plugs to trim. Either method can be finished off with a light sanding.
(For more on pocket hole joinery, read Rockler's article, Pocket hole Joinery with the Kreg Jig).