Skewer

A skewer occurs when two enemy targets are aligned and a rook, bishop, or queen attacks the one in front. The front piece is normally more valuable or required to respond, so it moves away and exposes the rear target.

The most forcing case places the king in front. A check must be answered, and if the king has to move, the piece behind it may become available for capture. A queen can also be the front target, provided that moving it cannot save the rear piece at the same time.

A skewer is the reverse image of a pin. In a pin, the front piece tends to remain because it protects something more important. In a skewer, the important piece is in front and its movement uncovers the target behind it.

Alignment alone is not enough. The front piece may be able to capture the attacker, block the line, move with a decisive threat, or defend the rear target. The final capture must also be checked for safety and counterplay.

The motif is related to an x-ray attack because pressure extends through an intervening piece. Skewer, however, specifically describes the sequence in which the front target moves and leaves the rear one accessible.