Correct

铁紧

/ tiě jǐn / 
Strokes

Example

As an Adjective

very tight

1
Shìqing
事情
mán
瞒
de
得
tiě
铁
jǐn
紧
  
。

Secrecy was very strict. / There was total confidentiality.

2
Ménguān
门关
de
得
tiě
铁
jǐn
紧
  
。

The door was shut tight.