Historical clue formulations

• Doubly bent construction piece — 2015-10-08
• Letter-shaped beam — 2011-04-05
• Letter-shaped beam — 2007-09-19
• Construction piece shaped like the last letter of the alphabet — 2005-07-21
• Letter-shaped construction piece — 2002-01-14
• Letter-shaped construction piece — 2000-08-13