When making clothes or costumes or even pieces of armor it helps to have a pattern piece. I usually make my own patterns. One of my greatest aids is a roll of brown paper.
I sketch it out on brown paper, then trace it on to the fabric or metal or leather.
If you are making a piece that is symmetrical it will come out a lot better if you fold it down the middle and cut out both sides at once. This will ensure that both halves look the same.
Fold the paper in half, cut the paper out.
Mark which side of the paper faces out or up.
When the piece is placed on the leather, I use an ice pick to poke holes through the pattern piece where the rivets will be.
Even the rivet holes will line up if you fold the paper in half, then make the holes instead of marking each side by themselves.
The lines on the paper pattern piece show where the rivets will go. This may seem a bit OCD but the final result will look a lot better. Same thing, mark one side really perfectly, then fold the paper in half, to mark the other half exactly the same.
The first piece of leather mounted with perfectly spaced rivets. A paper pattern piece is a great way to experiment, make mistakes, and finalize a design before actually cutting expensive fabric, metal or leather.
Use some paper, make your own pattern pieces.
Go ahead, make a mess, make a pattern, have some fun