A bowl might curve outside the rink boundary on its path, but must arrive at rest inside the rink boundary to remain in play. Bowls slipping in the ditch are useless and removed from Perform, except within the event when a single has "touched" the jack on its way. "Touchers" https://webheights.co.uk/the-ultimate-guide-to-cat-bowls-elevated-raised-and-more/