I don't like using my thumbnail to open the battery door, so I'm going to attempt(!) a description of how I open it without -- both A (the harder way) and B (the easy way). Either way, click five times first to turn off (because otherwise, you're going to be firing like whoa).
A. Your hands must be dry/non-slippery. If you are right-handed: hold the Jac flat in your left hand with your fingers extended (your drip tip is pointed toward computer screen; mod body is vertical and parallel to keyboard), and your left hand thumb holding it down. Place your right hand, fingertips pointing left, horizontally over the top of the whole mod (and over your left thumb) so that the back of your knuckles are approximately over where the door connects with the body. Your right index finger is at the bottom of the mod, and your little finger is at the top. Your right thumb is is under the mod and pushing up. Your left thumb, at the top of the mod is pushing down.
Push down with the backs of your fingers and pull to the right. It will take a couple of tries, but once you get it, it's pretty easy to get the hang of it.
B. You have a rubber kitchen glove hanging around handy because you are constantly having to twist off difficult atties, etc. You grab the kitchen glove (you don't even have to put it on) and pull off the battery door. Fin.
A. Your hands must be dry/non-slippery. If you are right-handed: hold the Jac flat in your left hand with your fingers extended (your drip tip is pointed toward computer screen; mod body is vertical and parallel to keyboard), and your left hand thumb holding it down. Place your right hand, fingertips pointing left, horizontally over the top of the whole mod (and over your left thumb) so that the back of your knuckles are approximately over where the door connects with the body. Your right index finger is at the bottom of the mod, and your little finger is at the top. Your right thumb is is under the mod and pushing up. Your left thumb, at the top of the mod is pushing down.
Push down with the backs of your fingers and pull to the right. It will take a couple of tries, but once you get it, it's pretty easy to get the hang of it.
B. You have a rubber kitchen glove hanging around handy because you are constantly having to twist off difficult atties, etc. You grab the kitchen glove (you don't even have to put it on) and pull off the battery door. Fin.