We do that at training school.
We put our dogs in down/sit or stand, tell them to stay walk away, and hold the dogs in that position.
Our handler walks or jogs in between dogs and handlers.
Or she drags a big stuffed toy in between us.
The trainer also does a whistle as the dogs are in down stay.
The dogs do look the first time, but with a firm 'LEAVE' they soon get the message.
It's all part of training (well mine anyway), just has to be fun also.
I know your training is real training, but I still get the result I want....eventually


Mazz
