PURPOSE: To increase usability, by providing a plastic torque-aid plate in the handle of a key to freely project to the outside of the key and extending the plate by fingers when unlocking so as to rotate it with a weak force.

CONSTITUTION: A plastic torque-aid plate 2 is attached to the handle of a metallic key 1 to freely project to the outside of the key 1. The key 1 is inserted in the keyhole to extend the torque-aid plate 2 by fingers and rotate the plate in order to unlock with a weak force. The plate 2 is devised to be automatically contained in the key 1 when releasing fingers therefrom. In this way, the width of key can be made slender and smart and also the usability is increased.