I'd like to get some advice on how to extend many lines

[Joseph_Oster]

Get boundary from curves

The curves don’t touch each other? So you need to Extend Curve and then find intersection points. However, your curves are not all co-planar so they don’t all intersect. You can project them to a plane and then it will work: [boundary_curves_2021Feb1a] boundary_curves_2021Feb1a.gh (6.5 KB) Getting rectangles from this is another step… Several ways to do it but it’s a little more complicated and they won’t be where you have them now.

But this doesn’t solve all issues, such as what to do about overlapping lines.