You “pin” an opponents piece when you use a queen, rook, or bishop to attack a valuable piece “through” a less valuable “interposing” piece. This forces the pinned, interposing piece to remain still: moving it would expose the piece behind it to attack. Once a piece is pinned, it is often worthwhile to pile more attackers on the helplessly immobile piece.
Here’s an example:
This is a position that emerges from an opening called the Riga variation of the Ruy Lopez. No need to remember that – we won’t be studying openings in depth here at Patzer Chess. For the curious, though, it’s worth Googling.
Here moving the rook to e1 (Re1) pins black’s knight at e4. The knight can’t move, because moving the knight would expose the king to an attack from white’s rook. This pin, in fact, is called a “royal pin” or an “absolute pin,” because it is actually illegal for black to move in such a way that would expose its king to an attack.
Now black can pile the attacks on black’s knight (say, moving the Queen to d3, or the knight to d3) , which must remain helplessly still until the pin is removed (say, by moving black’s bishop to e7, putting another piece between the knight and king).
Let’s look at some other examples:
In this diagram, white has a royal pin on the knight at e6. At the same time, black has a “relative” pin (or just a “pin”) on white’s knight at f4. Moving the knight would expose white’s rook to an attack from black’s bishop.
Pins emerge quite often in chess. A pin can often help you remove an attack threat from one of your pieces by holding the attacking piece immobile. Combined with the other tactics we’ll cover over the next several weeks, pins can be one of the most valuable tactical elements in your repertoire.