Tricky Rules 1
What should happen if a bowl or jack at rest on your rink is likely to be hit by a bowl from a neighbouring rink?
LAW 37.6 Possible Bowl Displacement
Provided that it is clear that the bowl that will be hit is NOT likely to have an influence on the outcome of the head (ie not play a part in the count) a player at the head where the resting bowl sits (usually the Third or Skip) can choose whether to lift the bowl at rest and then replace it when the bowl coming from the neighbouring rink has passed, OR stop the bowl from the neighbouring rink. Otherwise the bowl from the neighbouring rink should be stopped.
In a singles game, the marker on the rink where the resting bowl sits should in all cases stop the bowl from the neighbouring rink.
If the bowl that is stopped was delivered on a bias that would have taken it back to its own rink, it should be returned to the player who delivered it to be replayed.
LAW 38.6 Possible Jack Displacement
In all cases the bowl from the neighbouring rink should be stopped by the marker (in a singles game) or any player at the head where the jack sits.