Chain Selection in Skin Tool doesn't work

[aset1106]

I'm complete beginner in Alias, so don't blame me much for my awkward explanation. My problem is: I'm trying to connect side surface of a car and wheelarch with Skin Tool. But Chain Select (in Skin Tool options) doesn't work for side surface (it's a Plane trimmed with curves). However on wheelarch Chain Select is working properly. 

[duaxiong]

Chain Select will fail if your COSs are not at least G1 in continuity.

[aset1106]

Thank you very much for reply! But with regard to COS continuity, what does it mean  exactly: "COSs must be G1 or higher"? It must have not more than 1 span? And how many degrees?  (Sorry, I'm not strong in Alias' theory yet)

[duaxiong]

For Continuity, please refer to this:

https://knowledge.autodesk.com/support/alias-products/getting-started/caas/CloudHelp/cloudhelp/2016/...

In general, if your projection curves are Aligned, the resulting projected COSs should also be within tolerance.

It is also possible to Align the COSs directly using the Align2008 tool, but this is less controllable.