Here is the process I normally use to check the edge with a marker. Before I get my stone ready, I put a black mark along the edge of both sides of the razor. While this is drying, I get the stone ready and if I am working on a wedge, add one piece of tape to the spine.
Once the marker is dry, I make one slow pass up the stone and one slow pass down. Immediately take a look at the edge. Any spot of marker that has not been removed, on both sides, will be your area of concern.
Pay attention to where the mark is located and slowly move the blade up or down the stone to try and find the correct stroke to remove the mark. Once you find it, do the same with the other side.
Re-mark the edge, let it dry, and try the test again, only this time compensate for the removal. If your extreme edge has no marking on it, then you have found the stroke you will need to hone this razor from beginning to end. If not, keep going until you do.
There is one situation where you might find 2 or 3 spots along the same edge where the marker isn't coming off. This calls for a different remedy. If you see this condition, cut a piece of tape, that is the same length as the unremoved marker, and place it directly above the mark. Cut the tape so it doesn't wrap around the spine to the other side. Do this for each mark and on both sides if necessary. On top of this put one full piece of tape down the spine to cover these pieces. Start to hone the razor and you will see the bevel created very evenly now and you should also see the dark lines disappear.
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Ray