Here's what the finished product looks like.

Getting materials together.

Putting some waterproof glue on the bottles.

Hammering in a metal loop.

Some special touches.

Anchor

Cutting some netting to fit over the bottles.

Stapling on the netting.

Hammering in the staples.

Here's the attachment for the clothesline

Extras - step.

Extras - pvc pipe

Here I've attached a pet carrier for a nest.