How to trim Breps?

Hi!

I am looking for help with trimming the breps as they meet, meaning…

  1. I have the steel and timber elements structure. The steel connects timber. I currently vary extend of timber elements with the slider, so when the slier is 80, then the timber elements do now overlap:

  2. However, in the above the steel plate is shown. I need my timber to coverup steel. With slider = 1, it looks like below.

It is totally not manufacturable therefore I need this timber to trim itself as it meets with the other piece of timber. I appreciate it is a very long question but maybe someone would have some suggestions? I need timber to slot like here(green-timber, red-steel:image