Explanation

In the following examples, the black g-pawn blocks Rxh7#. In a way, the g-pawn is pinned to the checkmate square h7. In each example, White has a way to force the g-pawn to move:

In the first diagram, the white knight can capture the black knight with 1.Nxh6. If Black recaptures with 1...gxh6, the seventh rank is opened and White can deliver checkmate with 2.Rxh7#.

In the second diagram, h6 is an empty square, but White can sacrifice the queen with 1.Qh6+!, forcing Black to capture it and open the seventh rank: 1...gxh6 2.Rh7#.

In the third diagram, the black h-pawn is on h7, but White can play 1.Qh6! anyway, threatening Qxh7#. Black can defend against the checkmate threat with 1...gxh6, but again this opens the seventh rank for 2.Rxh7#—and 1...g6 2.Rxh7# (or Qxh7#) doesn't help either.

Examples

Black can open the line for the rook from a2 to h2 with the queen sacrifice 1...Qh3+!. White is forced to capture the queen with 2.gxh3, and Black can checkmate with 2...Rh2#.

White can open the line for the pawn from e6 to e7 with the knight sacrifice 1.Nf6+!. Black is forced to capture the knight with 1...Bxf6, and White can deliver a discovered Boden's mate with 2.e7#.

Black can open the line for the rook from f8 to f1 with the queen sacrifice 1...Qxg2+!. White is forced to capture the queen with 2.Rxg2. The rook is also deflected from protecting f1, and Black can checkmate with 2...Rf1#.

How to Spot Opening a Line for Checkmate

This is a very common checkmate combination that often includes sacrificing material—but it can be tricky to spot. If a possible checkmate is blocked by one of your opponent's pieces, think of ways to force the blocking piece to move.

Related motifs

A line can also be opened for the checkmate attack (instead of for the checkmate move).
It is also possible to open a line for a fork, or for a capture (use the pin).