I took this pic of a t-lid I have handy. The lamp wire is fed through the hole on the driver side of the lid, following the route of the green line I drew at "1". The lamp bracket screws on at "2".
The lamp works off a gravity switch inside the lamp. I don't know if these lamps are a mercury switch or some kind of moving ball or cylinder inside it that makes the contact. When the trunklid is the up position, the mechanism in the switch moves to a position that makes a ground connection, and light goes on. When down the mechanism opens the ground and the light goes out.
