The dog here is extreamly nervous and is therefore held on a lead all the time. Normally the lead is realesed at the same moment the sound begins. The dog should have the possibility to escape as far as it wants.
When the dog has passed the arrangement to make the noise ( a collection of wheel caps falling down on some corrugated sheet ) the wheel caps are released .
The sound should come from behind the dog, it has been found that this gives the dog improved possibilitys to work with its entire spectrum of characteristics. Nearly all dogs catapults a shorter or longer distance, this is not important since a lively dog of course reacts more powerfully than a slow dog. What is important is the time it takes for the dog to recover from the fear, if it can investigate the cause of the noise by its own powers or if it needs support from the handler. If it rapidly forgets about the noise generator when it has found out about it or if it nervously expects further supprises to happen.