Have a look at
this. I found it doing a search of this site, and it came from
here.
Don't use the tracing method on page three. I'd use the mitre cut method on page four. I'd cut it from the top and not the bottom. I'd use a handsaw for the straight part. Undercut it a bit so theirs a slight acute angle at the front edge. When you push it hard against the abutting piece it should be nice and tight. But before you cut it, check that the piece that you're butting against is square from the floor. If it's not you can adjust your mitre cut to suit by checking the angle with a bevel.
