In horse racing what is a flag start?

In horse racing, a flag start is employed when it is impossible, for whatever reason, to use starting stalls or a starting tape. In emergency circumstances, including, but not limited to, starting equipment failure, less than the requisite number of stalls handlers being available or the ground being sufficiently soft to prevent the manoeuvre of starting stalls, any race may be started by flag, subject to approval by the starter or stewards. During a flag start, the starter mounts the starting rostrum and, when he wants the horses to walk forward, he signals to the jockeys by raising his flag. Horses in the front rank must only walk, or jig jog, until the starter lowers his flag, thereby effecting the start of the race.