Historical clue formulations

• Letter-shaped groove for a fastener — 2026-06-02
• Letter-shaped opening — 2025-07-13
• Letter-shaped opening for a bolt — 2024-07-01
• Letter-shaped groove used in framing — 2024-02-11
• Groove for a letter-shaped bolt — 2023-08-08
• Letter-shaped opening in hardware — 2023-01-17
• Letter-shaped opening for a bolt — 2020-07-15
• Letter-shaped opening — 2020-04-25
• Opening for 31-Down — 2019-02-15
• Letter-shaped track in metalworking — 2017-09-04
• A weather strip may fit into it — 2012-02-10
• Groove for a letter-shaped bolt — 2009-02-04
• Letter-shaped opening for a bolt — 2008-01-01
• Letter-shaped opening — 2004-11-19
• Letter-shaped opening — 2002-02-02