A pin attacks a piece that cannot move without exposing a more valuable piece behind it. When that piece is the king the pin is absolute and the pinned piece cannot legally move.
Key principles
- Bishops, rooks and queens pin along their lines
- Attack a pinned piece again: it cannot run
- A relative pin can be broken, but at a price
Common mistakes
- Moving a relatively pinned piece and losing the piece behind
- Pinning a piece that can simply be defended