how do you open to replace batteries?

when hook is not employed, at top of hook you will notice illustration of lock and direction to slide back to slide open

Well I bet if you look really hard at the flashlight, you will find that there are only three screws on the backside, the side that has the hanger on it. Just undo those three screws, lift that section off and you will see three AAA batteries there in the middle. Remember to put the negative end of the battery (the flat side) against the springs. Put the cover back on, put the screws in, do not over tighten, and check the lights operation. All should go well if you used fresh batteries.