Forty Thieves Solitaire is a very popular 2-deck solitaire game which is equally difficult to win. The objective of the game is to move all cards from the tableau to the foundation.
At the beginning 10 tableau piles are dealt 4 cards each face-up and remaining cards are set aside to form a stock pile. Foundations are build up by suit from Ace to King.
Tableau is built down by suit and only the top card in a tableau pile is available for play. Empty tableau pile can be filled with any card. Cards from the stock pile can be dealt to waste pile one at a time which can then be played to a foundation or tableau pile. Only one pass can be made for dealing cards from the stock pile to the waste pile.