Who is Brother Salvatore (Brother Knuckles) from Brother Odd and what is their importance?

Brother Salvatore (Knuckles) is the only one other than Father Bernard and Mother Angela who knows Odd's secret. Brother Knuckles is also the Abbey's cellarer, keeping an inventory of and purchasing the food and other material goods that the monastery and the school require. Having traded his life in New Jersey for this life at the monastery, Brother Knuckles has lost the edge of violence with which he came arrived at the Abbey.