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 . Countersniper teams `` will be familiar with every potential threat , '' according to the Secret Service . 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 does n'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 . Watch countersniper detail up-close » . Unit commander Lt. Bernard Hall jokingly calls the weapon a JAR -- `` Just Another Rifle . '' Since the unit formed in 1971 , the unit has never had to fire a JAR to safeguard a person they are assigned to protect . `` When you look at that parade on the day of the inauguration , every building that we will pass by ... has been surveyed , and that is done by the Countersniper Team , '' said Secret Service director Mark Sullivan . `` They will be familiar with every building ; they will be familiar with every potential threat . '' But the absence of gunfire -- a welcome absence in this line of work -- does n't mean they have never identified or mitigated a threat , Sullivan says . The teams typically consist of two people , both armed with high-powered rifles , either of whom can shoot to deter an imminent threat . If one countersniper spots a threat , that person prepares to shoot while the other member takes on the role of `` wind caller , '' telling the shooter how to adjust his aim to counteract the wind . The wind caller takes cues from chimney smoke , flags or undulations from the atmosphere . At a firing range outside of Washington , the team demonstrates its skills in a variety of positions . Both men peer through high-powered binoculars looking for threats . `` Watch the threat area , '' an instructor shouts . Thirty seconds pass before a target pops up down range . One of the countersnipers drops his binoculars and reaches for his weapon , shouting to his colleague . `` Left side . Left side , '' the wind reader responds . The shooter fires one shot . `` Center ! In the middle , '' the instructor reports . While the countersnipers can scan the crowds below , their focus is on looking for places where snipers might be concealed , team members say . All countersnipers go through nine weeks of intense training . Half of those who try out for the team fail . Fewer than 200 people have been assigned to the unit in its 30-plus year history , the service says . There are fewer than 100 countersnipers in the unit , a Secret Service spokesman says . This is n't a job for someone who ca n't handle extreme temperatures . The cold can be biting ; the heat , blistering . Hall said officers have tricks for keeping mental focus in inclement weather . `` When it 's hot , we 're probably thinking about the cold days in January . When it 's cold , we 're probably thinking about August , '' he said . On Tuesday , in addition to the snipers , an estimated 8,000 police officers will be on duty , along with almost 1,000 FBI personnel , Transportation Security Administration screeners and others , including 10,000 National Guard troops . The Department of Homeland Security has said that another 20,000 members of the National Guard are being held in reserve . `` I think we are ready , '' said Homeland Security Secretary Michael Chertoff . `` I do n't anticipate anything disruptive . Part of my job is to hope for the best and plan for the worst . ''
Countersniper teams to be out in force across Washington for Inauguration Day . `` They will be familiar with every potential threat , '' director says . The Secret Service formed the elite unit in 1971 . Homeland security chief says agency is prepared .