walls have ears; sliding doors have eyes
Proverb meaning that secrets can easily leak out; one should be careful what one says, as someone may be listening or watching. Often used as a warning. Part of the longer proverb 壁に耳あり障子に目あり.
See also: 壁に耳あり障子に目あり
They say 'sliding doors have eyes,' so let's not talk secrets here.
A traditional Japanese proverb. The exact origin is uncertain, but it reflects the idea that in traditional Japanese houses with paper sliding doors (障子), sounds and sights can pass through easily.