To put it simply it’s a multiple navel piercing project where two navel piercings are joined together using a single barbell.
You can have either one or even two navel industrials in your belly button. If you go for the second option, your piercings will resemble a cross.
But as you can imagine, the belly button is subject to quite a wide range of movements. After all it’s the waistline and when you lean forward or sit down the skin folds around your navel push together. So it would be a wise idea to insert separate belly button rings in both (or four if you go for a double-navel industrial) fresh belly piercing holes.
If you want to go for a single barbell straight away, it would be wise to choose at least some flexible belly industrial piercing – PTFE barbell is the best option for this purpose. You can cut it to size and then screw the balls on. The shaft is self-threading and the piercer won’t have any problems with getting it done.
By the way, read this navel industrial piercing story. The piercer did something I wouldn’t have done – he just bent a simple barbell and inserted it into the fresh navel industrial project! The girl was very happy with the piercing though, and it seems the healing process was OK.
However, I warmly suggest if you go for a navel industrial piercing, get at least this PTFE barbell inserted. But, of course, you can also go for separate belly rings in each hole while the piercing heals, and insert the industrial barbell when the fresh navel piercings have properly healed in about a couple of months.