外側

1. Origins, structure, and basic meaning

• Structure: 外側, read そとがわ, combines outside with a side or surface.
• Basic usage: It denotes the outer surface or outside side of something with a distinguishable inside and outside.

2. Common pitfalls and similar expressions

• A reference object is required
  • 箱の外側 and 窓の外側 identify the object whose outside is meant with the noun before の.
• Location marked by に
  • In both marking and attaching examples, 外側に identifies where the mark or board is placed.