I got it by hitting the yellow birds straight through the small wooden blocks in the middle of the cement walls. If you hit it at the right angle and time the birds burst of speed right you can fly through all the walls
level 7 is hard:icon_evil:
I haven't been playing it as much (playing WordFued a lot, when I get a few games going and keep playing...), but still trying to get past the last few last parts of level 7 is hard! And I've been trying to avoid Tips about Angry Birds to get past them... when I finally do it's nice. However, as I'm playing them I keep thinking I will ask for a tip. And I probably will...
On a side note, I follow Pauley Perrette on Twitter who's on the TV show NCIS (plays Abby) and said :
Wow. How many people are in #Ineedtherapy because of #angrybirds 2 of my costars are two of them!