Betting & odds
Lay
To lay a horse is to bet against it, accepting the stake of somebody backing it and paying out if it wins. Laying is available to ordinary punters on betting exchanges, where the layer's risk is the stake multiplied by the odds minus one. A false-favourite signal is often read as a lay signal, but the exchange commission and the margin on short-priced runners make laying favourites far less profitable than it looks.
In use
Laying a $3.00 favourite for $100 risks $200 to win $100.
On FormRace
FormRace flags favourites the model rates as vulnerable, but publishes them as a research signal — not a lay recommendation.