Greco’s mate makes use of ideas similar to those just seen, but executes them on a different diagonal-and-file pair. You use the king’s bishop (i.e., the light-squared bishop if you are playing the White pieces) to put pressure on g8 rather than h8; then you use a queen or rook to seal off the h-file and leave the castled king nowhere to go—resulting in the checkmate we observe in skeletal form to the left. Notice the similarity in structure to Morphy’s mate. There the g-file was sealed off by a rook or queen; here it’s the h-file. There the long diagonal leading to h8 was dominated by a bishop; here it’s the diagonal leading to g8. The general idea of trapping the king with coordinated diagonal and vertical pressure is the same, though in this case the sacrifices typically needed to open the needed file look a little different.