If there is a grid of tubes on the back, there are no lines in the sides. If not, carefully cut a hole through the inside liner where you want to put the line, then move the insulation out of the way and look for a line welded to the outside skin.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk