[knowaveragejoe]

I wish this went into a bit more detail about working with the mirror itself. Do you actually need a 2-way mirror? Or can you simply use something with that coating on one side?

[hannahmitt]

Some mirrors may have a thin enough back coating for light to shine through, but the two-way is ideal.

[IanCal]

I'm not too sure what you're asking, but a two way mirror is just a surface that reflects some light and lets some through. It's a very thin metallic coating on one side of something transparent.