In this instructable I'll go through the steps of building an acoustic guitar strap with a small number of tools.
You will need:
Step 1: Hook
At this point, you need to get a small piece of pvc and cut it in half.
Then you heat it until it gets flexible enough to enable it to become flat.
I used two angle grinder disks to perform this task.
Once the pvc is flat, you need to cut halfway (and keep both pieces).
One of the pvc pieces will become the hook that holds the guitar.
To create the hook, you need to re-heat the pvc and fold it at +- 1/3 of its length.
Again I used the disks to do this.
Finally, you need to create the loop for the string.
Re-heat the long part of the folded pvc piece and roll it around a screw.
In my first attempt, I used thin screw and I had trouble passing the string.
You can now sand the hook so it looks nice and doesn't damage the guitar.
Step 2: Adjuster
This one is pretty straightforward.
You pick the other pvc piece, drill 3 holes in it, sand it, and tadahhh, done!