Attach two docking ports together in VAB?

[Epistellar]

Is it possible?

[Syd Khaos]

Yup yup!
Just be aware that the attachment is only as strong as if they were docked outside the VAB.

[Epistellar]

I can't seem to line them up? Two docking ports, face to face, don't react with one another.

[Syd Khaos]

What ports are you trying to do this with?
Docking ports should have attach node at docking point in VAB. You may need to view from side in VAB to make sure the nodes are clicking together and your not surface attaching one to the other.

[Quivico]

Don't forget to also hold down alt and align them properly.

[AlexMBrennan]

I can't seem to line them up? Two docking ports, face to face, don't react with one another.

Not sure, but it is possible that you are doing this the wrong way - in the VAB, you need to place stuff one piece at a time: Place the docking port on main ship, then place a (rotated) docking port attached to that, and then attach whatever parts you want.
If you have a pre-built ship with a docking port and wish to attach that to another docking port it will, most likely, not work because KSP only lets you attach the root part.

Further, the rockets you build in the VAB have to have a tree structure, which means it is not possible to have e.g. bicouplers with two docking ports, and have BOTH ports connected (which is easy to work around since you can just use a ton of struts to hold them in place during launch, and quickly detatch and reattach them once you've made orbit)