Turton doubling is a manoeuvre in chess in which a piece moves along a line (rank, file or diagonal), 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. Use of the term is effectively limited to the field of chess problems, although it happens in real games a well (especially when White moves the bishop on d3 back to let the queen in front to threaten Qh7#, and analogous for Black). Turton doubling can be contrasted with another form of doubling, Zepler doubling.