The term 'heavy string' can refer to two different items: a CORD and TWINE. A CORD is a thick, strong rope made of several strands of material twisted together. It is often used for tying things together or for decoration. TWINE is a thin, flexible string made of two or more strands of material twisted together. It is often used for tying packages, securing items, or for crafts. Both CORD and TWINE are considered heavy strings because they are strong and durable.