That is because it is a floating ground...
From: Adam Moffett
Sent: Friday, February 9, 2018 4:15 PM
Subject: Re: [AFMUG] tying down wires
Someone who knows what it is might try grounding with it. And they'll complain
you didn't include the screws.
------ Original Message ------
Sent: 2/9/2018 6:10:38 PM
Subject: [AFMUG] tying down wires
I wonder if I put one of these in the box:
with the screws removed, if that would be a suitable thing to tie off cables
coming into the box to?
(not sure the image will come through)