It's this dent/crack on the side near the end pin. I remember when this happened - I was at a friend's house and accidentally whacked the end of the guitar on the corner of a coffee table.
Since the sides are plywood, it's not a clean crack or break. It's like a combination of a dent and a crack. Another reason to have a solid wood instrument - even the breaks are better!
I couldn't reach into the guitar far enough to get to the dent, so I took a 3/8 inch dowel and ran it through the soundhole and pointed it at the dent from the inside.
There were mixed results. I thought I might be able to just push the whole thing out, but I couldn't. The different layers in the laminate were all cracked differently.
So I pushed it out as much as I could and then spread Titebond on the cracks while I kept it pushed out as much as I could.
Then I made a splint to go on the inside. It's cedar - I figure it's not worth cutting a hunk of mahogany for this. If it gets whacked again, it may just crack a little more, so I don't think it needs a strong piece behind it.
I used some repair magnets to hold the splint in place. Since I had to reach so far in, I stuck a magnet to the patch with masking tape. Then I used pliers to grip the magnet and move the whole thing inside the guitar until I had it where I wanted it.
The pliers, of course, stuck to the magnet, so they helped keep the splint aligned.
I put glue on the back surface of the splint - the one that will contact the side of the guitar on the inside.
Then, while I was guiding the inside magnet into place, I put its mate on the outside. It got pulled right up to the guitar - and I was able to use it to help guide the inside splint and magnet exactly where I wanted it.
The magnets are a real lifesaver for this sort of repair.
Really hard to get a good picture of the whole thing, but here it is.
I actually wound up using longer pliers than the shot above to be able to reach in.
The green arrow points to the magnet. I left everything as is overnight until the glue dried.
When it was dry, I slid the outside magnet off. The inside magnet was then freed up, and I could pull it out with the pliers. I left a long 'tail' on the tape so I could then just reach in and grab it and pull it out as well.
The upside-down view looking into the mirror inside the guitar. The repair came out very well - it's squared up nicely and I didn't get any glue runs.
Not, mind you, that anyone will ever look inside the guitar. But I know I did it the best I could.
You may have wondered how I got the interior of the guitar lit up. I cooked up a simple guitar "trouble light" with a bulb socket. It's just wired straight to an AC plug.
I have a CFL in it - a "75 watt" bulb. It doesn't get too warm at all and illuminates the inside very well. An incandescent would be too hot to sit inside a guitar, I think.