Is it possible to move relative position of GUI?

Hi i am making a sort of HUD layer by using OnGUI function for Android. However, there are lots of devices having different resolution. So I need to re-position controls in hud layer because OnGUI draws 2D things. I came up with re-position controls with adjusting rate of screen size like this. ex> GUI.Button(new Rect(Screen.width posx, Screen.height posY, Screen.width sizex, Screen.height sizeY); but it doesn't look good. their positions are not what I expected.

So, I tried another way to use drawing sprites with ortho camera. But in this case, i have to make a customized button.

I don't know how to do this.(I had only 2 weeks experience with Unity.

Anyone have a good idea? Thanks.