suggestion box; comment box
A box for collecting opinions, suggestions, or feedback, commonly found in offices, schools, or public facilities.
A suggestion box was installed in the company lobby.
The students put their opinions in the comment box.
complaints box (Edo period, at the supreme court)
Historical term for a box placed in front of the supreme court during the Edo period, where commoners could submit complaints or petitions.
During the Edo period, the complaints box was a way for commoners to convey their voices to the shogunate.
Compound of 目安 (めやす, 'guide' or 'standard') and 箱 (はこ, 'box'). The historical sense refers to a specific complaints box used in the Edo period.