Pick what you are sharpening, get the angle, and see exactly how high to lift the spine. No guesswork.
Your sharpening angle is set by how high you hold the spine above the stone. The math is simple: lift height equals blade width multiplied by the sine of the angle. A 2 inch wide chef knife held at 20 degrees needs the spine about 0.68 inches off the stone. Most people hold their first guess too steep, which makes edges thick and dull faster.
The coin trick makes it physical. Stack the listed coins under the spine, feel that height with your guide hand, then keep it as you sharpen. Quarters run about 1.75 mm thick and nickels about 1.95 mm, so a small stack gets you surprisingly close.
Factory angles differ by maker. Shun grinds at 16 degrees per side and Wusthof’s PEtec edge is 14. Matching the factory angle keeps the bevel a single clean plane, which means less metal removed and faster sharpening.