Here is a goal: How can you tell if you are in a room with a one way or 2 way mirror?

How would you accomplish this goal?

Choose your answer from:
+ Place your fingernail against the ceiling, if there is a gap (small distance) between the nail and it's reflection, it's a regular mirror if it touches the mirror directly without even a small gap you are in a room with a 1 way mirror, leave now.;
+ Place your fingernail against the mirror, if there is a gap (small distance) between the nail and it's reflection, it's a regular mirror if it touches the mirror directly without even a small gap you are in a room with a 1 way mirror, leave now.;
Place your fingernail against the mirror, if there is a gap (small distance) between the nail and it's reflection, it's a regular mirror if it touches the mirror directly without even a small gap you are in a room with a 1 way mirror, leave now.