this is the sensor, and the job that the sensor does is to scan the area where the garage door opens and shuts to make sure that there are no obstacles in the way when the door is activated to either close or open. chunks of meat or particularly tasty treats are ideal because they have a stronger influence over your dog than normal treats would. i found him trimming bushes, his deadly-looking shears slicing the twigs and leaves, making them fly everywhere. remember that it is also useful to display a price list of your products. 