tap at

tap at something

to make one or more light blows on something. Fred tapped at the door, but no one heard him. Who is tapping at my window?
See also: tap
References in classic literature ?
Bucketful by bucketful, from the tap at the sink in the corner, he filled a large galvanized-iron tub.
His tap at the glass roused her from the musing solitude in which she sat, and she came to the door to open it; aiding her steps with a little crutch-stick.
Presently, however, he heard a light tap at his door, then the door opened slowly, and he could see the flash of Lady Arabella's white dress through the opening.
Carbide offers the potential of higher cutting speeds and lifetimes of 100 to 500 times the life of a conventional tap at about ten times its cost, Matysiak says.