So when I was putting this strip together in 1997, I had a horrible time drawing straight lines with my mechanical ink pens. The lines would always leave streaks when you pulled the ruler away from the paper, so I used stuff called "border tape." The tape is essentially a slick transparent tape with a design down the middle — in this case a simple straight line.
The problem was, I couldn't even get that right. I could never make the lines meet exactly, so my borders still looked awful.
Geez, what's a guy to do? Well, getting a proper ruler helped. Years later, I found a nice ruler with cork attached to the back. It worked just fine. More commonly, a wooden ruler with an implanted straight edge works too.

By the way, of all my Joe Fuhr comics, I hate this punchline the most. Geez, it's lame.