There are *4 large pockets on each of the wide side, *6 large/small
pockets on each of the narrow side.
The frame adopts 2*2cm square tubes, which is very strong.
The wire diameter of pockets is 4.5mm, which can hold even
heavy books. Moreover, the inclination angle of them is precisely
designed, and the wide and narrow sides can be perfectly fitted,
which is convenient for storage and transportation.
