The knight fork

A single knight move can create two threats.

A square that attacks both targets

Mark both targets and find a square from which a knight attacks both. Then check whether your knight can reach that square in one legal move.

When the fork gives check

A fork with check forces the opponent to deal with the check first. Look for a legal capture of the knight, then see whether you can take the queen after each reply.

Evaluate the position after the capture

After a capture, count the remaining material and look for threats. A fork can win an advantage, but the position after the exchange determines what that advantage is worth.

Sources

• FIDE Laws of Chess