Zepler doubling is a manoeuvre in chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

 in which a piece moves along a certain line (rank, file or diagonal), then another friendly piece moves onto that same line, then the first piece moves again in the same direction as before. The term is effectively limited to the field of chess problem

Chess problem

A chess problem, also called a chess composition, is a puzzle set by somebody using chess pieces on a chess board, that presents the solver with a particular task to be achieved. For instance, a position might be given with the instruction that White is to move first, and checkmate Black in two...

s.

The first problem to show the idea (shown to the right), by Erich Zepler

Erich Zepler

Erich Ernest Zepler , later known as Eric, was a German-born electronics expert and chess problem composer....

 himself, is a simple and clear demonstration of the manoeuvre. The straightforward doubling 1.Rgb2, threatening 2.Rb8#, fails to 1...Bxd6, so the more roundabout Zepler doubling is required: 1.Rb4 Bg7 (now 1...Bxd6 is no good because of 2.Rg8+) 2.Rgb2 any 3.Rb8#.

Zepler doubling can be contrasted with another doubling manoeuvre, Turton doubling

Turton doubling

Turton doubling is a manoeuvre in chess in which a piece moves along a line , then a similarly-moving piece moves onto the same line in front of it, then this second piece moves again along this line, in the opposite direction to that of the first...

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