Historical clue formulations

• Make airtight — 2018-08-05
• Close tightly — 2017-12-31
• Close tightly — 2017-08-21
• Shrink-wrap, e.g. — 2015-09-26
• Close tightly — 2004-12-13
• Make airtight — 2000-10-15
• Close tight — 2000-05-13
• Thoroughly confine — 1998-08-09