Tao Teh Ching Chapter 11

三十辐共一毂，当其无，有车之用。埏埴以为器，当其无，有器之用。凿户牖以为室，当其无，有室之用。
故有之以为利，无之以为用。

Translation
(A carriage has) 30 spokes that shares the same nave, but it is when it has the voidness (the axis) that it has the function of a carriage; Mix water and clay to make a jug, but it is because the empty space that has the function of a jug; Make windows and doors so a house is built, but it is when the emptiness of the is formed that a house can has its function.
Therefore to have is for the profit and to not have is for the function.

Detailed Comment
I have to admit I stumbled with this seemingly easy chapter. Literally, this is a quite simple chapter, however I am trying hard to figure out what Lao Tzu is trying to tell us.
The three analogies talks about one thing, that is only the voidness created from non-voidness has the function and is the reason for the non-voidness to exist. It is believed that voidness is the essential character of all beings in Buddhism. I find it very hard to understand 利, or profit, here. Why is it to have is for the profit? I am trying to understand the whole paragraph like this:
The essential teaching is that everything is created out of nothing. Let's look at any object, scientist say they are made of atoms, and atoms are made of electrons and neutrons etc. What is the neutron made of? Perhaps quacks. Ok, let's agree that, but what is quack made of? This question can go on and on. Science can never answer this. This is a philosophical question. On and on, we will have to conclude that matter is made of nothing, i.e. We are made of nothing. Secondly, we are told that atoms are bind together through "bonds". Now what is a "bond"? As a chemistry student, I take bond for granted. Now that I think about it, it seems to me that the "bond" is made of nothing and it is essentially void. The fact is, without the bonds, the atoms cannot form anything. 当其无，有原子之用. Therefore the voidness is the origin of all things.