[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/US/01/19/sniper.training/art.snipers.cnn.jpg caption="Countersniper teams will be familiar with every potential threat, according to the Secret Service."]
WASHINGTON (CNN) - Look up at any presidential event and you're likely to see them: men dressed in black, armed to the teeth, looking back.
It's no secret; they're with the Secret Service.
On Tuesday at the inauguration, members of the U.S. Secret Service's elite countersniper unit will be out in force, taking roof-top positions along Pennsylvania Avenue and elsewhere as the presidential motorcade glides past throngs of people for the swearing in of Barack Obama.
The Secret Service doesn't mind you knowing they are up there. In fact, their mere presence at the inauguration has a deterrent effect, they say. But they are mum about many other details, including how many teams will be deployed, how long they work and about their custom firearms.