Draw the shield shape you want on the cardboard with a ruler and pencil.
Cut out the shape of the shield with scissors.
Decorate the shield with pigment or colored paper, and you can draw your favorite patterns and signs.
Cut a rectangular opening on the back of the shield with scissors, which can be used to clamp the shield.
According to the need, cut a few small holes near the edge of the shield, tie a rope or elastic band to hold the shield and keep it stable.