을지 모르다

don't know whether or what

Marks something as genuinely unsettled. With a question word it is 'I don't know what' — 근데 아침엔 추웠어. 뭐 입을지 모르겠더라 'I didn't know what to wear.' Doubled as 을지 없을지 it is 'whether or not': 아저씨가 너 클 때까지 방송을 하고 있을지 없을지 모르겠다. With 모르니까 it becomes a reason to be careful: 뭘 밟을지 모르니까 바닥 잘 보고요 'you never know what you'll step on, so watch the floor.'