Video: Gary and Mayhem
Schutzhund is a German sport that involves three progressively more difficult levels of tracking and protection.  It was designed around the turn of the century as a breeder's test for German Shepherds.  Sometimes a young dog having a Schutzhund title can indicate that it is appropriate for police work but needs to carefully evaluate that as it is possible for a good trainer to get a weaker dog through the test.  The protection portion requires the dog to search 2, 4 and then 6 blinds to find the "helper" (decoy) and then bark and hold.  The handler approaches and calls the dog out, whereupon the handler then downs the dog and gets out of sight into the blind.  The helper then runs and the dog must catch him.  This is followed a long courage test, where dog and helper charge each other.