Test Corner Points: watch this video featuring products available on petco.com.
First, verify that the flag locations are within range limits of the system. Place the corner flag at the minimum and maximum distance points of your desired boundaries and test these flags to be sure they are within the acceptable 15 to 19 feet of the transmitter. Point the arrow on the receiver mounting bracket in the directions away from the transmitter. Stand still with the receiver caller while testing these corner flags. The BPU will show the distance of each flag in feet from the transmitter.