The knife sharpener that keeps a good knife good.

This is the tool that does the most for the least. Wusthof forges the rod from high carbon stainless steel tempered to 58 HRC, the same hardness it lists for its Classic knives, and cuts light grooves along its length. The rod is magnetic, so the fine particles it lifts off the edge stay on the steel rather than your food.

Use it every few times you cook. Hold the knife at about its edge angle, draw it down the rod a few times on each side, lightly, and the edge comes back into line. Nine inches is enough for an eight inch chef's knife and short enough for a drawer.

Skip it for hard Japanese knives around 60 HRC and above. A grooved steel as hard or softer than the blade does little, and the grooves can chip a thin, hard edge. Those knives want the ceramic rod or a fine stone.

Ceramic is harder than any kitchen knife steel, so a ceramic rod does a little real sharpening as it hones. That makes it the right daily tool for Japanese knives and for German knives that have gone past what a plain steel can fix. Wusthof describes its 10 inch ceramic rod as suited to dull to moderately sharp knives.

The extra inch over the steel above helps with longer blades, and the smooth surface is kinder to thin edges than grooves. Use the same light touch: a few strokes each side, at the knife's own angle, before cooking rather than after.

Ceramic is brittle. A drop onto stone can crack or snap the rod, so hang it or keep it in a block slot. Skip it if every knife in the house is German and in good order; the steel is enough.

A whetstone is the slowest option and the best one. It removes the least metal, works at whatever angle you hold, and handles every knife in the house, German or Japanese. This Shun stone has a 1000 grit side to set the edge and a 6000 grit side to polish it, and comes with a rubber tray that holds it steady on the counter.

Soak it in water first, as Shun directs. Then work the 1000 side until you raise a small burr along the whole edge, switch to the 6000 side, and finish with light strokes. Shun sharpens its own double bevel knives at 16 degrees, a sensible target for most Japanese blades.

The learning curve is real, and the first few sessions are slow. Skip it if you will not give it twenty minutes and some patience. A Shun owner who would rather not learn can use Shun's mail-in service instead, which sharpens free for original owners who bought from authorized dealers, with a $15 processing fee in the US.

This is the ProntoPro, model 4643, from the Pennsylvania company that has made Chef'sChoice sharpeners since 1984. It uses diamond abrasive wheels in fixed angle guides: one stage for 15 degree Asian style blades, one for 20 degree European and American blades, and a polishing stage that also handles serrated knives.

Most cheap pull-throughs have one fixed angle and carbide blades that tear at an edge. This one lets you match the knife, which matters in a house with both a German chef's knife and a Japanese santoku. A few light pulls restore a working edge.

It still removes more metal than a stone, and it is no tool for single bevel Japanese knives. Skip it if you own one very good knife and are willing to learn a whetstone.

The 1520 AngleSelect has three stages. The first sharpens 15 degree knives, the second 20 degree knives, and the third uses flexible stropping disks to polish either. Chef'sChoice says a first sharpening takes about a minute and a touch up about ten seconds.

That speed is the point. It turns sharpening from a project into something done before a dinner party, and the precision guides hold the angle from heel to tip. It handles serrated knives in the last stage and weighs about 4.4 pounds, so it sits on a shelf rather than in a drawer.

The trade is metal. A motorized diamond wheel takes off more steel than a stone, and a heavy hand shortens a knife's life. Skip it for expensive single bevel or very hard Japanese blades, which belong on a stone or with the maker's service.

If you are buying a stone and a rod anyway, this is the tidy way to do it. The kit pairs Shun's 1000/6000 combination whetstone with a 9 inch stainless honing steel and an angled bamboo stand that holds both.

The steel has a smooth side and a finely ribbed side. Shun's listing suggests the smooth side weekly and the ribbed side monthly, which suits Shun's harder blades better than a coarse grooved steel would. The stand helps with angle as you hone.

Skip it if you already own a ceramic rod, or if your knives are all German; the Wusthof steel and the stone alone cost less and do the same job.