What is the meaning of ?

a chain

the closing and locking of a door or gate

a door or gate so closed and locked

a bar or other device used to lock a door or gate

a connection, linkage, or continuation

a chain

a string of items tied together

the part of the opening of a drawstring bag through which the string is passed

a metal bar used to lock shut a gate, door, chest, or other opening

a key used to lock or unlock such an opening

a pill or tablet

Source: wiktionary.org