 Shells are used decoratively in many ways . They can be pressed into concrete or plaster to make decorative paths , steps or walls and can be used to embellish picture frames , mirrors or other craft items . They can be stacked up and glued together to make ornaments . They can be pierced and threaded onto necklaces or made into other forms of jewellery . Shells have had various uses in the past as body decorations , utensils , scrapers and cutting implements . Carefully cut and shaped shell tools dating back 32 @,@ 000 years have been found in a cave in Indonesia . In this region , shell technology may have been developed in preference to the use of stone or bone implements , perhaps because of the scarcity of suitable rock materials . 
