Are you referring to this one?
If so I'd advise against it. The sharpener in left slot is a carbide "ripper". It will sharpen/reprofile a blade but it's very hard on it and removes a lot of metal. Knives tend to "chatter" across these sharpeners, giving you an edge that's almost serrated-looking under magnification. The other slot is a sort of mini ceramic crock stick; it will work better and remove less metal.
Those of you who are long time DC'ers will probably groan at this, since I repeat it so often (
) but I usually recommend the Edgemaker Pro
to people who need sharp knives but don't want to mess with stones. A whole set of 3 is only about $30, and most people can get by with just the Red (or the Red & Yellow). Here's a couple of images of them:
Unlike carbide rippers, the Edgemakers use rods of different grits. When you run the knife thru them they flex a bit, applying leverage while cutting. Press hard and they'll remove more metal while a light touch removes very little. The yellow "Handy Honer" is very fine, and feels completely smooth to the touch- it will put a shaving edge on a blade with minimal wear. My dad has knives that have been heavily used and sharpened only on the yellow, and after 15 years there's little discernable wear. On the other hand, my brother has a chef's knife sharpened for 10 years on nothing but a "ripper", and it took me half an hour with a super-coarse DMT diamond stone to get it to the point where I could sharpen it with a coarse waterstone! That's how much damage they do.
The Edgemaker Pro has a very simple learning curve. I could hand one to any home cook and teach them how to put a shaving-sharp edge on any decent knife in a just a few minutes. The Blue is extremely coarse, so much so that you'll almost never use it; the only purpose is extremely dull knives or garden tools (works great on hoes and lawn mower blades). The Red has two different grits, a medium and a fine. This will suffice for most knives. But the Yellow is the real gem, the secret to getting a great edge. A light touch with the Yellow will impart an edge that will fillet paper, assuming you have a good knife. If you use it regularly you'll never need the others.
Lastly, no- I don't get paid to shill them!
I use waterstones for my best knives, and prefer my Edge Pro Apex for getting toasty edges. I also use a Spyderco Sharpmaker along with ceramic & glass hones. But I always keep my Edgemaker Pro's in my knife roll. They're perfect for touchups and great for the "house knives" that restaurants generally keep for the staff.