We understand that the battery compartment on our OnGuard handheld training device can be somewhat tricky to open, and we are here to help. You'll see on the bottom of the device that there are 2 arrows near the slide.
While holding the OnGuard with one hand, use your other thumb to move that slide in the direction of the arrow marked with a number 1. While the slide is in that position, push it towards the arrow marked with a number 2. Then you'll be able to flip that bottom piece up and insert your batteries.