Holes in 64 stepside bed rails?

[Breadstick]

I don't know why, but I have very small holes drilled in the side of the bed rails on my 64 stepside. They are all lined up and about 4-5 inches apart. I have no idea why they would be there. Could they have been for the snap on bed top?

I have searched every parts website and this site a lot and can't find any kind of trim piece that would go there, so I'm thinking someone put something aftermarket on it. Does anyone have any ideas? I can't figure out why someone would put something so cheap on something so beautiful.