Joining Edge Problem

[aldyandanah]

Hello, i was trying to make a solid object by joining some naked edges. but in the end, there is 1 naked edge that cant be joined. Any solution for this? thank youB3-35.3dm (273.6 KB)

[Tone]

extrude a to b. At the moment the surface generating the naked edge creates a bad surface (if you explode everything and try joining just that bit of edge to the circular flat surface, you should see the problem).

[aldyandanah]

thank you very much