What needs to be written about a spinner blade? A bunch, I believe. And you should know it all. There are three basic styles of spinner blades, and several others that do not fit any of the standards.

There’s a new, dumb trend: the fidget spinner. It’s a toy like a top, but spun in the hand rather than on a surface. The user holds a pad at the center, and flicks one of three rounded blades. The ...