In order to save time, if a player thinks his ball might be lost or out of bounds, they may play a back-up or 'provisional ball'.

This must be played after the fellow golfers have played their shots and before going to look for it.

If the original ball is found within the five minutes, the player must carry on with it even if it is in an unplayable lie and pick up the provisional.

If the original is not found, the provisional becomes the ball in play.