如何在故事板或xib中选择背景视图

If I select a view with my mouse in a storyboard or xib, Xcode will select the front most view. I know that I can select the other views in the document outline, but if I want to grab a background view to move it with my mouse, the front most view gets selected again when I click in the storyboard.If I select a view with my mouse in a storyboar