noun
metal cap; ferrule
A metal fitting that caps or reinforces the end of an object, such as a walking stick, umbrella tip, or brush handle.
この杖の口金が外れてしまった。
The metal cap on this walking stick has come off.
The clasp on the coin purse broke, and the wallet won't close.
noun
The mouthpiece of a wind instrument or a similar part that contacts the mouth.
トランペットの口金を消毒してください。
Please disinfect the trumpet mouthpiece.
noun
socket; light socket
A socket for a light bulb or similar electrical component.
電球を口金にしっかり差し込んでください。
Please insert the light bulb firmly into the socket.