It is Extremely hard to explain how to make this complicated bag but here's my attempt:

To make a bag that looks like this, you need:
- 2 small silver D-rings
- 3 small black buckles
- 2 pads for shoulder straps
- 1 long, thin strap
- a few other items that need to be made like the round cap on top of the bag




PART ONE:
The bag

1. You need a simple black bag:
   
    
2. when you have the basic shape, you need the outside triangular piece
   
   To make it you need buckles and a piece of leather that's been cut like the shape above,
   
   Click to enlarge
   
   ...and the buckles attached to it with duct tape.
   
   
   
   here you can see one side of the Velcro on top of the back of the plastic buckle. this will attach to the bag.
    
3. After you make this you need the top round cap that's on the bag this can be made out of Duct tape and covered with pleather. and attach it to the bag using Velcro such as this:
   
   
   PART TWO:
   The front of the bag
   
   
   You need to cut out some leather into this shape:
   
   Then make two cuts in the middle, where the centre strap will go through it. (you need two of these)
   
   You need another small piece of strap to go through the centre strap and have a metal D-ring sowed onto the end, all this attached onto the shoulder pads.
   
    
4. The centre strap is laced with Velcro and can open and close by putting one on top of the other
   
   Hopefully this helps and what you end up with is this:
5.