I came across these really well done videos regarding sharpening. We get a fair number of I can't sharpen my "fillintheknife" so it must be the knife threads so I thought I'd post a link. I think of sharpening as an artform- it takes practice to be good at it and it helps to know the theory behind it. The videos are great for any newbies or those who are sharpening impaired. He covers convexing in depth as well as the basic methods for sharpening.