In Roppongi Hills 2

傘ふり場、　ここで傘をお振りください
かさふりじょ、　ここでかさをおふりください
Umbrella shaking place, please shake your umbrella here.

On a rainy day in Japan, the sheer volume of people with umbrellas can create a flood inside a shopping area, so you have to shake your umbrella or put it in a plastic bag. And there are special places to shake it, and sometimes special electrostatic machines which attract the shaken water. Of course I never do it.