 Henry, close the barn door. You ever done this before? Partly. Okay, this is the cathode. Here's where the light rays get converted to an electron image. The first step is we gotta get the cathode stuck into one of those glass tube blanks that you borrowed from the university. The heavy wires are the leads. The leads? You gotta seal the leads through the wall of the tube, glass to metal. Uh-huh. Get a firm hold. Now, slip it in. Slip it in? The cathode. I guess about a half inch from the end?