下敷き

1. Origins, structure, and basic meaning

• Structure: Spelling: 下敷き. Reading: したじき. Core meaning: writing mat; being pinned under.
• Basic usage: Representative examples: 柔らかい机なので紙の下に下敷きを置いた / 棚が倒れても下敷きにならないよう十分に距離を取った.

2. Common pitfalls and similar expressions

• Writing mat and pinned state
  • The object placed under paper is 下敷き, while being pinned beneath a fallen object is 下敷きになる. The second use describes a dangerous spatial state, not the stationery item.