Tao Te Ching Says:

Thirty spokes on a cartwheel.

Go towards the hub that is the centre.

-but look, there is nothing at the centre
and that is precisely why it works!

If you mould a cup you have to make a hallow:
it is the emptiness within it that makes it useful.

In a house or room it is the empty spaces
-the doors, the windows - that make it useable.

They all use what they are made of
to do what they do,

but without their nothingness they would be nothing.