Kickstand

[AZwldcats]

If ypu look at the Teardown: HTC Evo 4G Teardown - iFixit

I think it is as close to center that it can be without sacrificing the battery.

And if you look at this pic: http://guide-images.ifixit.net/igi/YNVGMNNw4Vx2hwBd.huge

Could it maybe be the antenna for the Wifi? The wifi is the red box on the right top here
http://guide-images.ifixit.net/igi/gBPuLxjHbmBSFKqi.huge

 

[Mustachio]

Do you mean the phone Vertically instead of horizontally?

yes

 

[mr.seth.price]

It closes on mine if I use it (vertical) this way as well. Never even thought to try since I'd rather hold it in that position and not usually watching videos that way.