Clip release on the upper-left of the receiver can be pushed inward from outside the rifle. This pushes the inside of the release OUTward, the thing being pivoted in the middle.
As the Follower rises, it trips the Clip Release from within the mag well of the rifle. Once the release is tripped, the little spring throws the clip far and wide and you hear a loud PINGGG! Your enemy also knows that your rifle now is empty. Helpful information just everywhere!
Sorry no gif available here.
Try a copy of Julian S. Hatcher's BOOK OF THE GARAND.... or zip over to milsurps dot com, take out a free membership and raid their Military Knowledge Library for your own pdf of the original MANUAL.
Hope this helps.
.