HELP........ What is this cursor icon!?

Excuse the horrible photo. I couldn't get print screen to capture the cursor!
Does anyone know what this symbol means? It pops up on my cursor around certain bits of the designs i've been working on recently, never seen it before..... It's generally when I hover to the side of the selected object. But it doesn't seem to do anything?
Any help would be greatly appreciated!
Thanks.
