I had an opportunity to pick up a nice Jansport external frame backpack at a very reasonable price at a garage sale. I really like it, however there are several parts of the pack that I don't understand exactly what they are for.

I've attached a photograph of it with the parts in question highlighted in yellow.

1) There is a semicircle set of zippered teeth with a zipper pull that has nothing to attach to it. I assume I'm missing something that would have the corresponding teeth so it could be zippered/attached to the back - possibly a hydration pack? Any ideas what this might be?
ear the bottom with several

2) There are 2 clips on each side on the back that appear to connect together, however the lengths are WAYYY short. It appears as though this is where a strap would connect across the back of the full pack to cinch it tight, - so am I missing the extra straps?

3) Lastly, there is the hard rubber portion near the bottom with slits - my assumption is that these are slits where I could attach more items using straps again, but I'm not positive.

Can anyone give me some expert advice? I love the pack, but I want to make sure I'm using every option available to me.

First, let me say I have no personal familiarity with this pack, so I will be guessing, based only on general knowledge. I think you are basically correct in all your surmises.

The 1) and 2) features are probably related. But even if you knew what your missing piece was, it would still be missing.

You could piece together some new straps to fit those 2) clips, if you thought you needed them for something.

AS for 3), you are spot on. That's for adding straps, but I wouldn't strap anything particularly heavy to them. Whatever is hanging out there will bounce as you walk and put a lot of stress on the attachments.

My extremely wild guess (I haven't looked at a Jansport pack for many years) would be that there was an add-on compartment, perhaps a zip-off day pack, that fastened on with that zipper and those clips. I really think that it was meant to detach, or Jansport wouldn't have put a tag on the underneath surface. Whatever it was probably added another pound of weight to the pack itself. Any weight in it would tend to pull the pack away from your back, not a good idea. I very much doubt it was for hydration; water is heavy and should be as close to your back as possible. I suspect the former owner ditched that extra compartment or whatever it was a long time ago, with good reason IMHO.

Re #3, a lot of packs have those stupid heavy plastic things to run straps through. They add to the weight of the pack and are not something you'd want to use. Again, anything tied back there would tend to pull the weight away from your back, and would also catch on brush as you hike.

If it were mine, I'd whack off the excess zipper and clips and (if possible without ruining the fabric it's attached to) the patch, in the interest of reducing weight. But, as we often say here, Your Mileage May Vary!

You have demonstrated very well that it's definitely worth searching for gear in thrift stores and garage sales! But make sure that the pack is comfortable for you with a full load before you take it out on a trip.

Thank you both very much for your help! I was sorta on the right track it looks like, but you both make a good point that anything additional added to the back will definitely cause issues with weight transfer, etc... so I think I'll quit worrying about what was supposed to be attached there

Much appreciated!!

Those plastic black tabs on the bottom are useless as the others have pointed out. The get old and crack so go ahead and remove them using a seam ripper or a small pocket knife. Just be careful.

I'd also remove the buckles and make some straps with them.

I'd leave the zipper and find a mating zipper and make a mesh pocket to attach or just sew one on (probably less weight and hassle). It's nice to have a mesh pocket to store wet things in.

My son has carried the Jansport Scout for 5 years now and many miles and loves it. We did upgrade it with a set of shoulder straps and hip pad from the Carson model.

I like the front loading option that yours seems to have.

Nice find!

Several Jansport models have a zip-off daypack. The zipper and clips are for the daypack. Not having the daypack is no great loss.