Free Castling Rule

An interesting chess variant is Free Castling Rule.

The Dictionary of Modern Chess indicates that this was played in 17th Century Rome.

Rules

1. When castling, the King may be placed on any square up to & including the Rook's square and vice versa.
2. The King & Rook must still end up to the right of the Rook in Kingside castling (and the left of the Rook in Queenside castling).
3. Check may not be given by castling.

Examples

Here white may castle Queenside and black may castle Kingside.

This is one possible way white and black may castle under these rules.

The most popular Kingside castle in Free Castling involves moving the king to the h-file and the rook to the f-file.

Shown is yet another way white and black may castle.

There are many more possibilities.

Sources

Dictionary of Modern Chess, Byrne J Horton 1959.

Diagrams were made with Chess Captor.