When you build a Heavy Watt Wire first and build an Airlock on top of it, you can basically build a HW Wire through a "wall". Whole process is shown in the below video, as well as things that don't work while this one method does work.
Steps to Reproduce
Build Heavy Watt Wire, finish building it, build airlock over it.
Status: Known Issue
We are aware of this issue and have it logged internally but either we do not have a fix ready yet or we are not planning on addressing the issue in the immediate future.