'don't know one's place': describes a disrespectful behavior towards an elder, normally a saying from an elder to the youngster who disrespects them
Definitions (粵典–words.hk)
語句
話人不分尊卑，唔識得顧忌下自己嘅身份地位，又唔尊重其他人 used to criticise someone for lacking respect, for not respecting hierarchy and status; literally "no superior and inferior relationship"
你敢搶老細嘢食？冇大冇細！
你敢抢老细嘢食？冇大冇细！
nei5 gam2 coeng2 lou5 sai3 je5 sik6? mou5 daai6 mou5 sai3! How dare you take snacks away from your boss! No sense of hierarchy!
Definitions (Wiktionary)
phrase, Cantonese, Xiang, idiomatic
to have no sense of who is senior and who is junior; to show no respect to elders (syn.) 冒大冒細, 無上無下, 不上不下, 沒大沒小, 無老無大, 十裡八搭, 嘸大小, 冇上冇下, 無大無細, 沒大小, 嘸大嘸小, 冇大冇小, 冇得大細, 無大無小, 冇大冇細, 沒老沒少