Keep an eye on your teammate as he climbs his way to the top of buildings to defuse planted bombs. As a sniper, shoot down any threats that cross your teammate's path and make sure that he stays safe until he reaches the top of that building. Use your mouse to point and your left mouse button to shoot. Watch for enemies hiding behind open windows; exterminate them when their eyes flash out of the window before they drop something on your team member's head. Enemies could be lurking behind open doors as well. Finish them before they notice you.