Give Prop Physics which doesn't have Physics

I want to add Physics to Props which actually doesn’t have Physics.
How would I do that?

[editline]8th August 2015[/editline]

Okay Guys, I figured it out my own.

I used this two nice guys to add Physics to a Prop which doesnt have Physics^^

Any of these except the first one will do:

http://i.imgur.com/vw2P2PE.png