Originally Posted By lightweight
I'm new to backpacking and just bought my first external frame pack. The pack was used and has some type of mount on the top bar. Here's a pic: https://ibb.co/b2ZbOw What would this mount be used for? I tried Googling this, but came up empty, so any help you can offer will be greatly appreciated.

It looks like it was made by the owner in a machine shop. I have done my share of machining so I know the look.
Who knows what it could have been for? Looks like the frame was an old Jansport.