There's another thread on here about this, but Verizon did disable/hide this feature. However, if you download an app from the Play Store called Quickshortcutmaker, you can create a shortcut that points to the feature. And... you don't have to be rooted to get it to work.
I'm on Verizon and have created a shortcut to give me access to Blocking Mode. It works well. My only gripe with it so far is that it leaves an icon on the status bar that I'd rather not see. I've not found a way to get rid of it as Blocking Mode doesn't seem to have the option of not displaying it.