D.11 A STRIKE is a bowl delivered at such a speed as to attempt to negate the bias.
If you intend to strike, you must tell your opponent and make sure anyone on the green and any spectators are warned to move out of the path of your wood. If you strike more than once without giving a warning, it could cost you the game.
Reference From the Laws Of The Game
5.6 Players are required to give a verbal warning to their opponent and to take every precaution before striking, to eliminate the possibility of causing injury to other players, Referee, Measurers or spectators by being struck with a jack or bowls. A player shall receive a caution for the first transgression of this Law. For a second offence, the game shall be awarded to the opponent(s). The offender(s) to receive no further score and the opponent(s) to receive the maximum score.