Ground cloth under hammock

[Kingpin]

3x3 piece of Tyvek for me. Working well so far.

[LokoLobo]

I use a small tarp made out of the same material Frog-togg gear is made from. Water proof but light and not to bulky.
Also soft on the feet when ya get up.

[Dr1530]

$6 walmart tarp has been my go to with rocks to hold down the corners.

[Acer]

piece of 4 mil clear plastic about 3' x 3' when backpacking,,when car camping, about a 2' x 4' piece of nylon rubber backed boat carpet soft for da feet.

[unshavenman]

Nobody has mentioned this product yet.
I use a 2'x3' piece of TYPAR, which is a house wrap very similar to TYVEK, but one side isn't slippery like TYVEK.
It can be found in dumpsters at residential building sites as well which for me made it free!

[TGish]

I got a 4x6 tarp from harbor freight that works perfectly. And it's camo for some cool bonus points.