1.   She was woken by a sharp rap on the door.

2.   We heard a sharp rap on the door.

3.   There was a sharp rap on the door.

4.   I just tell him to shut up and give him a sharp rap across the knuckles.

5.   A few sharp raps on the table got their attention, but sometimes little else.

6.   A sharp rap of the hammer breaks off the protruding shell, allowing insertion of the knife in the resulting hole.

7.   Then suddenly, there was a sharp rap on my shoulder.

8.   Use a sharp rap of the knuckle and listen for a secondary vibration, or echo, underneath the main vibrato.