A busted bike inner tube
Bucket of water
Rotary cutter and cutting mat (optional)
Paperclips or binders clips
Hole punch or screw punch with punching mat
Darning needle or DIY needle made from a paper clip
Button (and needle and thread) or Velcro for closure
Tip: If you don’t have a busted tube, or want to make this project with a group and need more tubes, check at your local bike shop — chances are they’ll be happy to pass along some trash-bound tubes.