The 3d has a reservoir for liquid. When your wick starts going dry, you squonk/push the plunger for more liquid to get to the deck and wick. I haven't had this atty leak when deck is dry. I've kept my fill screw in it, so I can keep it in a bag when I'm out and about.
Edit- and when using it, my atomizers are at the same angle as tube mods.
37, ph0n3 h0m3.