Open-ended materials like stones, feathers, twigs, etc., are materials that can be used to build or create or to combine to make something new.  They provide multiple uses and endless play. They enable children to be creative and express themselves in play, often using materials to explore and represent other things. There is no pressure to complete an “end product” or be bound by limitations.  By exploring the materials, children become innovators, designers and explorers as they build, sort, design and stack in a variety of different ways. Playing by their own rules allows children to be creative and have fun.