During my wanderings in our basement, I took some pics of some knob and tube we have more for historical purposes since this nasty stuff is getting turned off and ripped out as soon as possible...
Here is an older porcelain light fixture with two knobs with a hot and neutral wire running through them to the fixture... yes the bulb is kinda just hanging from the cord below.. yikes!
Heres a picture of some tubes that again the neutral and hot wires are going through the tubes... see the nice safe Romex wiring behind it ...
Here's an oldie, but goodie...
See the wood piece next to the light switch (the picture is sideways)...
This was how K&T was originally ran through a house I think .. through wood pieces that had grooves cut into them. Two pieces would be put together so that the neutral and hot wires would be covered and seperated at the same time..
And yes, this lightswitch is still in use and running off of those wires in the picture...