[dirtboy]

The evil signholder could have it balanced on each forefinger with each thumb extended upward behind it, so the sign is slightly leaning back. But to have it stay that way would require no wind at all.

Well, then there's this picture:

The guy is walking with the sign - which would induce wind - and holding it the same way.

[Coop]

His index fingers are up a bit more in this second photo, thereby allowing a better grip. But it would still be tough to keep it balanced that way, especially while walking. Not impossible, but it sure seems curious.