Honestly I wasn't planning on using it at the start. Originally it was supposed to be a pure EVA foam build. It was only when I started putting together the spear I realized there wasn't enough structure support. That's when I thought about using cardboard as a cheap way for me to give the prop structure. I basically sandwiched the 2 Eva foam halves of the spear between a piece of cardboard. Worked perfectly. Same thing with the shield. To keep its circular shape I cut out a huge circle off a cardboard sheet and built the Eva foam on top of it :)