Why is there no universal hand sign for thank you ?

But the priest finally shook his head and gave the hand sign for "land."

She read his hand signs, however, nodded, and retreated into the kitchen.

Flags where for changing my style of run and making a hand sign.

With hand signs we were able to order (no menus).

He stood up in the cupola, made a hand sign: be ready.

His wrinkled hands came up and moved through smooth hand signs.

I asked, reading the usual meaning in that hand sign.

He replied with a hand sign of his own.

For it was only in those brown eyes that she saw confirmation of her own hand signs.