Can't join two straight lines that share a common point

Having an issue joining two surfaces that were constructed using one common line. Even when drilled down to deconstructing - reconstructing 3 points and trying to join two lines that share a similar point there is an issue. What is going on here?Surfaces and lines wont (24.6 KB)

You need to flatten the inputs.

Take a look here to learn about data trees:

Thanks again Michael, your the best. But I still don’t understand why
A) the original two ruled surfaces wouldn’t join?
B) and even stranger…why the individual lines that share a common point won’t join?

Everything in your file seems to join fine if you make the lists correct (flatten)

right, Definitely learned that the hard way. Thank you.