Do you have some magic script to select the edge loop on the poly-surface or to select all tangent edges to the preselected poly-surface edge?
Hi @mdesign, if a post selection is acceptable too, try _SelChain
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Or double click on an edge to select the edge loop.
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It works but it’s easy to miss the edge. That’s why I haven`t noticed it before.
I don’t get what you mean by that
btw: Ctrl+Shift double clicking an edge, you can also use this method for preselection
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I meant that you can point exactly to the edge line during clicking and it`s very easy not to hit the line. I miss edge picking every few clicks. Maybe I have bad eyes 
Thanks. I knew earlier that preselection.
What am I missing here? Here’s me double clicking the edge:
And here’s me ctrl+shift double clicking the edge after hiding the surface it was cycling through:
I have a nice script which extracts tangent surfaces from polysurfaces from this forum before. It would be nice to get something similar for duplicating tangend edges on polysurfaces too… 
do you have overlapping objects in that area? A sample file would be useful
sample.3dm (44.2 KB)
Sure. Double click on the edges of the planes at the end and it works. Double click on the blend surface in between and you’ll see the same behavior as in the gifs above.
99% of the time when I want to select tangent edges, I don’t have planes…
@eobet I see what you mean, this seems to work better in Rhino 8 with the added sub object highlight, but there it doesn’t work all the time either.
To make this reliable, you could use selection filter, so that only edges are selectable, then it works 100% of the time:
Rhino 8 with subobject highlight:
RH-77897 Ctrl+Shift+Double click edge selection does not work 100% of the time
Wow, and that option is only visible when you enable sub-object selection… which I never do so I didn’t know about it. 
Still, I’d actually like a script in this instance anyway, because then there could be a tolerance option added so you can go higher than the modeling tolerance (for when you are cleaning up imported surfaces, for example).
Does SelChain lack features to give you what you want?
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Ah, ok… it does! Two things confused me… for some reason, I had gotten it into my head that this command was only accessible once you’ve started another tool. Maybe because it’s mostly mentioned in that context on this forum. My mistake!
Second, not only had the imported surface I was working on up to 4 degrees of tangency deviation (much higher than I thought), but also micro edges which I didn’t notice until I zoomed way in… which is also why I thought it didn’t work.
So, all good. SelChain is now added to my permanent toolbar! 
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