Backpack frame and sleeping bag

Why not put washers under the screws until those nuts are flush with the top of the bolt? Or find the kind of nuts with rounded tops to put over the ends of the bolts. Take the nuts you have to Lowe’s or Home Depot and you can find the right size.

Those nuts are called “cap nuts”, and, yes, Lowes and Home Depot have them, typically in drawers with other speciality fasteners.  But those aren’t lock-nuts like the ones McHale used on the pack. I’d have a little concern that a non-lock nut would slowly loosen (but a lock washer or some Loctite applied to the threads would help).

Some electrical tape wrapped around the bolt ends would be quick, easy and last a pretty long time.  Always cut electrical tape with scissors instead of stretching it until it breaks.  The cleaner edge from cutting will stick more securely.

You could hacksaw off the excess threads and then sand it smooth.  That would weigh LESS instead of MORE.

Excellent suggestions, thank you!

On a wing and a prayer, I went to four different hardware stores and one local (not a box store) person suggested rubber screw protector caps. Never heard of them but they are a stretchy cap that fits over the bolt and nut. He fished around with a few different sizes and, voila, he found caps that fit tightly and securely.

Looks like you found a great solution.  Very easily reversible, too.

In case someone else needs a different answer, you could use Plasti-Dip to coat the threads.  I usually use it to create softer, grippier handles on my DIY UL saw blades and such, buy you could apply a few coats to those threads with a disposable paint brush or Q-tip, letting it dry between each coat.  About $9 a can.  Once opened, it dries out in 6 months.  I’ve also coated the tops of tent pegs to make them more visible and easier to push in by hand and the backs of razor blades for better cushioning an grip.

Those caps are nice. Certainly easier than using a hacksaw and more protective than more metal nuts/washers.