Run you finger over the nodal area on the sides you run your plane, if they are smooth and feel like the rest of the strip, the plane blade is fine. If there are chinks, bumps or any other perceptible bumps of any kind you need to sharpen the blade, this is the easiest way to see how sharp your blade is. My early rods had some visible glue lines near the nodes which were all related to not sharpening the blade often enough and not having a steep enough angle. Get in the habit of feeling the node or inspecting it under magnification. Your strips will thank you.