There is disclosed an apparatus for mooring a structure and/or tensioning a mooring line. The apparatus comprises: a guide portion for guiding a portion of a first mooring line, and a lock arrangement, wherein the apparatus provides a mooring line path, the lock arrangement being provided on an opposite side of the mooring line path from the guide portion, at least when the lock arrangement is in an unlocked configuration. When in a locked configuration at least a portion of the lock arrangement is provided in the mooring path.