2 d) "Books" and "Bookends"
to start animated and spoken presentation or, alternatively, continue reading below.
Black keys help you to play without looking at your hands unnecesarily so that you can keep your eyes UP on the music.
Notice how the black keys occur in groups of 2 or 3.
Sometimes I describe them as groups of 2 or 3 "black books" flanked by white "book ends".
Notice how the thumbs of both hands are "numbered ONE".
Also notice how the third finger - the middle, longest, finger - of the left hand plays the first black key in the "two-some" group of "black books" with the left 4 on the "bookend" up against the "three-some" group of "black books".
The Right 2 is also on the "bookend" up against the "three-some" group.
Please to 2e) Rhythmic Blocks.