Hi Beetle,

> Hi Michael，I never understand CSec.zip this plug-in usage and benefits, whether, for example, thank you!

If you have a set of uneven long rails, you can use CSec to generate some shorter profile curves from those long rails by planar cuts in the top view.

See here for an example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=849.9


Usually though it's easiest to just directly loft the long rails with one another rather than preparing a bunch of small profiles. But CSec could be useful if you're doing some custom rebuilding task where lofting the long rails directly doesn't work so well because they've got creases in them or something like that.

Basically you would use CSec if you had a situation where you were thinking "I wish I had a section curve running across these guide rails at this cut line".

- Michael