Odd Vertices When Using The Knife Tool When I use the knife tool on my mesh, any face connected to the cut becomes "incorrect". (I don't know the true term)



The underside of my mesh was smooth before I cut the mesh. Now, there are odd triangles that even appear in the render.
Have you tried the J "join" tool instead?

Here is a link to the Blender Reference Manual on Vertex tools

https://www.blender.org/manual/modeling/meshes/editing/vertices.html