"I wouldn't be without it!"
I always use this protective gadget when using my microplane grater. Even for relatively soft food like cheese, I use the slider - it presses the cheese against the grater and that means I can grate very quickly, without fear of rubbing my fingers on the (very sharp) grater, and all the cheese gets grated right down to the last sliver. It's the work of a momnet to cut the cheese (or whatever) into a block that fits inside the slider. Happy grating!