An html version of RookCorners.cql. Created by Gady Costeff and Lewis Stiller.

; Find all games in which the same rook visits all four corners of the board.

 :pgn heijden.pgn
 :output rookcorners.pgn
 :forany rook [rR] ; loop over the possible rooks
 (position $rook[a1]) 
 (position $rook[h1])
 (position $rook[h8])
 (position $rook[a8])

After executing this with "> cql RookCorners.cql" there are 35 studies found in the Harold van der Heijden Database 2015.
NB. When you see {MATCH} in the text, it means that cql has found the position asked for.

Below only 5 studies are presented: