Step 3: Make the Body Strap
Now we'll make the body strap, or the long strap that will go around your body.
Sand the inside of the strap channel on one of the female side release buckles so that it slides easily along the strap. This will involve sanding, then checking the fit, and repeating. You want to pay particular attention to any bumps or other grabbing/friction devices. Also, be careful not to sand too much off. You still want this buckle to be strong.
Slide the modified female side release buckle onto the strap.
Use the remaining side release buckle set to connect the ends of the strap.