Scale the templates up or down depending on the size of your dog; the same goes for the length of the elastic that secures the fin around the belly. Choose elastic in a shade that best matches your dog’s coat.
Make chipboard and felt fins using Shark Fin Templates I and II. Make a felt flap using Felt Flap Template.
Glue chipboard fins together, leaving flaps unattached. Glue felt fin II onto one side of chipboard, folding edges over top. Glue felt fin I onto other side. Fold chipboard flaps out in opposite directions.
Cut out about 21 inches of elastic. Glue one end of elastic to top of one folded flap. Glue 3 inches of Velcro to top of other folded flap, and then glue coordinating piece onto other end of elastic. Tack Velcro on with needle and thread for extra strength. Glue felt flap piece to bottom of cardboard flaps.