Why do those non-manifold (loose) vertices arise

Hi,

I’ve got a simple mesh and do several cuts with the knife tool.
can anyone tell me why i got this extra vertex sitting on top of the other one?
i’ve often got this ending up going over the whole mesh just to cleanup that mess.
i’d like to know how to avoid that kind of stuff

cheers christian

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No idea where that came from but doesn’t look like non-manifold geometry. It’s connected.

Select all, W -> remove doubles, and ctrl+N to remove double vertices (within the specified merge distance when the object scale is 1,1,1) and to put all faces pointing outwards.

thanks for the tip!

i would prefer to prevent the knife tool from acting like this in the first place though.
i’m not a big fan of merging by distance and maybe accidently merging vertices that should have stayed.

Maybe you didnt snap to vertex. When its snapping to vertex, that snapping box has red outline.