The debate was interrupted by a knuckle rap at the door.

I was more than a little surprised when I saw Lucy standing in the open doorway to the master bedroom pantomiming a knuckle rap and saying, "Knock, knock."

This drew a knuckle rap from John H. Sununu, the White House chief of staff, who said the President believes that the governors "have a strong grasp about what's going on in the country."

Cliff sledged another gun-blow for the driver; but this was no gentle knuckle rap.

There was a knuckle rap on the glass.

The Peers seconded with a chorus of knuckle raps.

LEO: Alistair Kidd in "Larbert," wherever that is, suggests that Steve's AxCrypt encryption advice requires a knuckle rap.

Nothing that would generate more than a knuckle rap and a small fine if I were the clumsy type and got caught at it.

Presently, he put on his mask of quiet efficiency, stood up and commanded their attention with a knuckle rap against the table.

It was a sharp knuckle rap.