How can I place a flower box on my window without drilling?

I really like window boxes, and would like one, but every guide I've come across tells you to drill supports on the side of your house. Not only is my house rented, but the outside wall is concrete with rocks embedded in it.

I have sliding windows and no outside sill, but there's an empty part (and always empty, the window doesn't slide into that part) of the (metal) window frame that is 40" long, an inch or less wide, and a cm high edge.

Is it possible for me to have a window box?

How can I place a flower box on my window without drilling?
LIQUID NAILS. . . . Construction Adhesive. . . . However Buy they correct tube though..for the application.. Such as if you have plastic to wood ... or ect. . . Just go to your local hardware store and purchase a caulking gun.. and how ever much exterior adhesive you will need .. You prolly can get a gun for less than 9 dollars and the glue/adhesive 2-3 dollars .. P.s. A tube goes a long way.. GOod Luck
Reply:You need to go to any dIY Store and ask for a pair of sky hooks.If you cant get them you need a self levelling sky bracket fitting is straght forward and youll be enjoying your window box in no time.
Reply:it depends how high your window is, but you could make a stand for it coming up from the ground.

it might not look as nice, but it would work
Reply:Are you on the first floor of your place? Given all the restrictions you have with your construction, I would say the only way you could do this is by putting your flower box on legs. You could go cheap and use patio stones for flat supports for the legs. If heavy enough, with dirt in it, the box should not move during winds.

To assure it stays in place ,you might consider a strip of double faced tape along the frame you describe, or if it is empty channel, a very small clamp or two to hold the box to the frame.