• Measure and cut a 15-inch length of galvanized wire using heavy duty fencing or steelworkers' pliers. (Fencing pliers are shown in the photo.)
• Make the wire as straight as possible before bending. It'll make bending the wire into the chassis shape a lot easier.

Hint: To make an accurate bend, clamp the needle nose pliers on the wire slightly behind the intended bend by approximately one wire width.

The large black line on the template indicates the outline for the bent wire chassis. Start bending the right guide, then work your way around the outline to the left guide, bending each corner in succession.

The first bend folds back 1/4-inch of the wire on itself to hide the sharp cut end. 

Save these bends for last. They create a cradle for the battery holder.

When finished, you should have one of these. Test the fit of the battery box and adjust the wire cradle to hold it tightly.