According to Leavitt, most women are using the wrong nail tools when it comes to DIY manicures. One of the top offenders? Your nail file.

Here’s why: The most common emery boards, like the ones you buy at the drugstore, have extremely tough grit. Nail files are identified by numbers — the higher the number, the finer the grit. Common nail files rank at 80 or 100, but Leavitt insists that’s too harsh. “I find those traditional emery boards shred the nail,” she says. Leavitt’s professional nail files fall between 180 and 320. “I say 180 is the lowest number you should ever file a natural nail,” she advises. To find a great emery board, Leavitt suggests checking out the ones sold at professional beauty stores.