Assertion: pinball knocker | /r/HasProperty | small solenoid-fired piston
Facets:
value: inside the machine
type: LOCATION
Source sentences:
text: A pinball knocker is a small solenoid-fired piston inside the machine which knocks against a mounting bracket, creating a loud “thwack” sound, in order to indicate when a high score has been beaten or that a free game has been won.