how to show 'dummy' ad in UI when using Simulator?

Any advice regarding how to show a dummy ad on the UI when working on the simulator?  i.e. developing the UI where you want something showing where the ad will be?  

If fact are all the banner ads the same height for example (across devices/different ad networks), as if no then the approach would have to cater for this no doubt.   What is the design approach for the UI if it changes, so take the worst cast height and try to be dynamic in terms of how other (non-ad) UI items are positioned.   Can you reliably get the bottom position of whatever ad is showing and start your own UI components from this point downwards?