A Quickie

The "old" idea is to use a small rock

But I hate the idea of carrying heavy rocks, so styrofoam is much better

good idea

Back in the day, we used to just pick up the stone from the ground – we didn't carry it. In which case, even styrofoam balls would be excess weight.

A lark's head attachment is indeed great for this, and can be done by just making a longish loop in your tart cord, then making the lark's head with said loop.

Stephen,

Good point on forming the larks head by simply making a longish loop in the tarp cord. In other words my photo shows a knot that isn't needed and only complicates an even simpler method.

The knot would only be needed if one's intention was to attach a loop (or loops) to the tarp (hanky) for future attachment to a tie out cord running to a stake.

On a side note, I think Tarptent chose a good name for their company. I don't think Hankytent would have sold as well.

Daryl