Tea timing

So, this is the other important line. On the plank next to the cup you can see the line I mentioned drawn at the edge of the plank and the curved line that has been drawn to mark one of the corners of this inset for the table top. I made up a piece of wood the same thickness as the depth of cut for my little groove cutting router bit. Then I taped a cutter knife blade to either side with the points evenly placed. That is the item on the plank. Now I mark around the whole perimeter following the pencil line with one blade while the other makes a mark outside of it. You can just see the knife cut if you zoom in by clicking on the photo.
Once I took a tea break between drawing the perimeter line with the pencil and making the knife marks. When I came back from the break I forgot all about this step and set to cutting the plank to the pencil line on the bandsaw. As I said, this is no good at all as the resulting cut just leaves you a plank the will fall through the hole in the middle of the table. Anyway, I only ruined one plank, but now I always make sure I follow the process right through to the knife cut marking. The knife cut is a little hard to see, but it gives a much more accurate indicator of where the cut should be.
I suppose there is a better technique than this, but for a one off shape and a finish within a millimeter or two, this is a useful way to get a panel the right size to fit in a hole of uneven shape and size.