Use constraint-based layout to position an HBox horizontally, and explicit sizing and positioning
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" height="300" width="600"> <mx:HBox id="hBox2" xmlns:mx="http://www.adobe.com/2006/mxml" left="30" right="30" y="150" height="100" /> </mx:Application>