敲门砖 (敲門磚) qiāomén zhuān

qiāomén zhuān set phrase a brick to knock on a door; to use a temporary expedient
Domain: Common Saying 俗语
Notes: (CC-CEDICT '敲門磚'; Guoyu '敲門磚'; Mathews 1931 '敲門磚', p. 100)