Checkmate by double checkIf two pieces are lined up in the same straight line, you can sometimes use a very dangerous type of a discovered check: a double check.
In double checks, not only the hidden piece attacks the king, but also the piece that moves. A deadly weapon!
Have a look at the example to see how this works.
The advantage of double checks is that they force the king to move. You don’t have to worry about your back piece being attacked, as you have with normal discoverd checks.
What do you have to do?
Use a double check to checkmate. Do you see two pieces lined up? Move the front piece to check the enemy king. The piece behind it is also checking the king. Make sure the king has no flight squares.