I have this kit from Deep Sea Cosmetics that I am totally in love with, and the nail block is the best I've ever used.
I've used other nail blocks from Sally's Beauty Supply and have loved those as well. You can find them fairly inexpensive. I figured I'd try this one because it was just a dollar.
I had to dig this out of the trash to take a pic of it with my phone. When I "used" this, it felt like I was taking an old vinyl record and rubbing it across my nails. It did absolutely NOTHING other than annoy the fool out of me. Not only because of the sound, but the feel.
I would definitely recommend something else over this any day. This is by far one of the worst products I've ever used from E.L.F. along with the painful Nourishing Cuticle Pen.