If you’ve enjoyed Japanese sake in Japan, chances are you’ve been served at least once in the way shown above: poured until it overflows glass and spills into something strategically placed below. As I explained in my July 26 column in The Japan Times, this is called sosogi-koboshi 注ぎ溢し and presents various challenges. How do you pick up such a full glass? Are you supposed to drink the overflow? And if so, first or last?
Very often, the receptacle below is a wooden square called a masu 升, which makes things even harder. (It’s not easy to wrap your lips around straight edges and pointy corners.) Actually, a masu the traditional measure for rice and other grains and is not meant to be drunk from.
Except, of course — and there are always exceptions — at certain types of celebrations when a barrel of sake is broken open . At these occasions, everyone is passed a new masu, usually branded with a mark for the company, organization or individuals being feted. You accept a portion of the sake in your masu, and then take the empty cup home as a souvenir.

Really, the only “right time” to drink from these wooden cups is when a new barrel of sake is broken open at a celebration.
Check out the column for a sake expert’s advice on what do do if you’re served this way, and an explanation about why not everyone likes such a generous pour.