Chessboard is a variation of Fortress Solitaire. It is played like Fortress except in this game, aces can be placed over kings and vice versa on the tableau rows.
A space is left in the middle for the aces, which when available, become the bases for the foundations. The foundations are each built up by suit from ace up to kings.
At the tableau rows, the top card (i.e. the fully exposed one) of each row is available for play on the foundations or in the tableau. Tableau building is up or down by suit as the player pleases. However, one card can be moved at a time, and building is round-the-corner, i.e. aces can be placed over kings and vice versa as mentioned above. Spaces can be filled with any available card.
The game is won when all cards are built onto the foundations.