Have difficulty closing the open polysurface!

I tried many ways close this open polysurface but they wouldn’t work. Can any one tell me what’s wrong with the file?Thanks!spoon.3dm|attachment (578.0 KB)

Hi @jdlai.tw
Looks like something went wrong with the upload. Could you try to re-upload the file? I’m sure someone will take a look :slight_smile:

spoon.3dm (578.0 KB) try this !thank you.

Hello - the border curve for the plane that closes the shape is not quite planar:


Thanks, Pascal!
Finally got the wrong place .Trying to fix it!