Tic-tac (also tick-tack and non-hyphenated variants) is a traditional method of signs used by bookmakers to communicate the odds of certain horses.
In 1999, only three practitioners were noted to be still working on the southern UK tracks – Micky 'Hokey' Stuart, Billie Brown and Rocky Roberts.
[1] A tic-tac man will usually wear bright white gloves to make his hand movements easily seen.
[2] A few simple examples of signals: Within the UK there are some regional variations in the signals, for example in the south odds of 6/4 are represented by the hand touching the opposite ear, giving the slang term "ear'ole", whereas the same odds are indicated in the north by the hand touching the opposite elbow ("half arm").
Essentially, bookmakers use tic-tac as a way of communicating between their staff and ensuring their odds are not vastly different from their competitors, an advantage the punters could otherwise exploit.