on your marks
on your mark(s)
Get to your starting positions; get ready to begin. OK, everyone, on your marks—we're about to begin!
See also: on
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
on your marksused to instruct competitors in a race to prepare themselves in the correct starting position.
Farlex Partner Idioms Dictionary © Farlex 2017