Inacurals

I am trying to figure out why my 3rd brake light aint working. In the hanes book the wiring diagram shows the wire from the 3rd brake light goes to a box symbol that has a j/c next to it. WTF is this electrical symbol??? (they dont give a symbols index). Then the wire continues to the underhood fuse box to fuse #37 which thankfully they dont show where fuse # are located. Im getting d/c readings up to the bulb housings when i depress the brake. So why dont the bulbs light??? thanks for your help.