First take one ring.
Add two rings through the first one.
Add a ring to these two.
Add two rings to the last one.
Add a ring to the upper two.
Again add two ring to the last one. You can go on like that for as long a chain as you wish.
We can now expand in the other direction by adding a ring to the lower right ring.
Add a ring to the two lower right now.
And finally add a ring to the upper two.