|First metal matters.|
Second, if you'd like to amplify your wireless power, what's about the signal of the router.
If the routers signal is weak, you have to amplify the routers signal.
And that's the first thing, I suggest to do.
You can simply put a self-made parabolic antenna onto the routers antenna and justify it to the right direction.
That's what I've done and it works.
Here is a link to such self-made parabolic antenna.
How to build:
Please send a reply, if you solved the problem !!!