I have a question about generating lines between intersected points

I am trying to make a parametric stick framed columns which finger jointed when it meets the cieling.

However, I ran into a problem that I can not connect the curves. 

I know it is because that I have the intersected points moved to the certain f(z) but my intention is not to have that but the height to follow the flexible column height.

My situation is very similar to shop's project for PS1 or bookcafe in Korea. Any good references will be very much appreciated!!!

Please, see the attached definition and feel free to give me any feed back.

Also, I always have a hard time understanding list items.

I would like to have some liberty on manipulating the intersected points!

Thank you sooo much this forum is sooo great and I am learning tons in my limited time.