Restless Knights
The Skewer
A skewer is a reversed pin. Now the more important piece is in front. When it moves out of harm's way (out of the line of attack), the piece behind it gets captured. The important piece that is attacked will frequently (but not always, though) be the king (after all, he is the most important piece), so when he moves out of the line of attack (out of check), he will expose some other piece (could be any piece, even a pawn) that will fall. Queens, rooks and bishops are the pieces who can skewer.
Tips for using the board below: If you tap the f3-square, that'll take you to the next game. C3 will take you back to the previous one. If you tap e7, that will flip the board. Note that once you've flipped the board, the functions don't flip, so e7 becomes d2, f3 becomes c6 and c3 becomes f6. Many more squares have functions, I'll let you discover them for yourself if you want to.
The king must move out of check (out of the line of attack) and then the knight falls.
Black has to move the rook in order not to lose it but the knight on e7 will fall.
The bishop skewers the king and rook. The king has to move out of the line of attack (out of check), and the bishops captures the rook. Note that although the king can recapture the bishop, White wins material (the so-called exchange).
The rooks skewers the royal couple, and gives check to his majesty. When the king moves out of check, the rook captures the queen.