I can't find the name for this kind of hole. It allows the release of the plate by just loosening the bolt a bit, without having to remove it completely.
Searches using "teardrop" or "hole with oblong" do not return the desired results.
$\begingroup$
$\endgroup$
$\begingroup$
$\endgroup$
I would call that a 'key hole'.
-
1$\begingroup$ Yup, everything I can find calls them "keyhole slots". $\endgroup$ – JMac Feb 1 '17 at 21:53
