Knife tool question 1

I have been reading the knife tool wiki and while it explains some things, however some things I do not understand

This mesh is a close up of a truss that I am having problems on as I don’t really know how Truss T joints (this is for a bridge) are made. Though beside that point I am having problems with the Knife tool.

I am trying to make what seems to be a very simple cut straight cut I press K and constrain using C as I want a straight cut

And this is the result

It does not cut all the way through the mesh, it seems to cut only the top faces of the mesh and in that only those that seem to be completely flat but then it misses even a flat face why does this happen? I even cut using limit selection to visible but it does not cut all the way through I think it is a simple cut. I have never used cut really and this is why but reality is, it is a tool I need to understand, can any one help me please.


I re-read the wiki a few times and managed to see, the cut through tool, the cut through button Z = Allow the cut to cut through obscure surfaces.


BTW got any zoomed out views