The ‘threads’ used by surgeons to close a wound, often in layers, at the end of an operation. They may also be used for other indications such as joining vessels, intestine or ducts, tying off bleeding vessels or repairing damaged organs. The traditional, natural, but unreliable, sutures made of catgut (absorbable) and silk (non-absorbable) have been replaced by synthetic polymers that can be tailor-made for their purpose of use. For example, non- biodegradeable polypropylene sutures are used for a permanent anastomosis between arteries, whereas absobable polyglactin sutures are ideal for suturing bowel together after resection (anastomosis). Modern sutures are all ‘swaged’ onto the needle, so there is no shoulder, and this allows smooth passage through the tissues.