grout: a thin mortar that can be poured and used to fill cracks in masonry or brickwork
plaster: a mixture of lime or gypsum with sand and water; hardens into a smooth solid; used to cover walls and ceilings
acolyte: someone who assists a priest or minister in a liturgical service; a cleric ordained in the highest of the minor orders in the Roman Catholic Church but not in the Anglican Church or the Eastern Orthodox Churches