The couch: g8 and c8
A couch horse (卧槽马) sits on the enemy's second back rank beside the palace — g8 or c8 against a king on e9. From the couch it checks the king AND covers the escape hatch e7. Here Black's own advisors jam d9 and f9, and the crossed soldier on e7 seals e8. Your horse is one jump away: a knight's check cannot be blocked — only the flight squares matter, and every one of them is shut. Find the jump into the trough.