Expanding weatherstrip

[Barrel]

My '33 Hot Rod Assembly Manual instructs me to "install a strip of expanding weatherstrip in front of the door openings on the angled 1.50" tubes. It may just be my age here but this seems ambiguous to me. I have the strip and I know what it's for but I'm just not sure which chassis tubes they mean. I would be very grateful if someone could post a photo of this.
Thank you,
Neil.