Not many sounds in life, and I include all urban and rural sounds, exceed in interest a knock at the door. Charles Lamb
You knock at the door of Reality. You shake your thought wings, loosen your shoulders, and open. Rumi
The traveler has to knock at every alien door to come to his own, and he has to wonder through all the outer worlds to reach the innermost shrine at the end. Rabindranath Tagore
Don't knock at a dead man's door and expect an answer. American Proverb
It is useless to knock at the door of a deaf man. Greek Proverb
If begging should unfortunately be thy lot, knock at the large gates only. Arabic Proverb