Self-sharpening block slots are effective at keeping your knives sharp since they do sharpen them every time you remove and replace the knife in the block. Though this is enough to help maintain their sharpness when the knife is used infrequently, it isn’t a replacement for traditional sharpening on knives used more often. The knives you use every day for prepping your meals will still need to be sharpened using a sharpening tool or a professional sharpening once in a while to maintain their edge and stay as sharp as you need them.