I think it's a heavy plastic curtain weighted down by the rod along the bottom. Probably covering the entrance to a parking garage or car wash. A couple of drunk guys monkeying around.
An employee at a car wash told me he heard screaming coming from the wash bay one day and when he looked up at the security camera he saw a bunch of naked dudes running around trying to escape the spray. They thought it'd be a fun way to cool off in the summer.
