"Anything/everything that wasn't nailed down" is an idiom meaning anything that could be moved. You'd normally hear this if someone's house was robbed: "They took everything that wasn't nailed down", ie. they stole as much as possible. When Lynette asked if Susan batted her eyes to get a reaction from Mike, Susan's response was to show she tried everything possible.

"Susan:Honey, I batted everything that wasn’t nailed down. I’m telling you …nothing. " I can see why this phrase would be difficult to understand. Susan was simply saying that she did everything to get a reaction from Mike, but nothing happened. A woman batting her eyes means she opens and closes them quickly to look attractive to men. So Susan batted everything that was not nailed down (obviously an exaggeration in her speech) but nothing happened.