a blind man sharpening a knife: it's getting sharp / soon
Saying俗语俗語
Two-part saying歇后语歇後語
Meaning
Said when something will happen soon. Humorous, a stock reply to "when will it be done?".
Wordplay
快了 (kuài le) means both "the blade is getting sharp" and "it will be soon"; the blind man can only guess from the time spent, so the phrase answers a question about timing.