#building_block.building_material__buildingblock  a block of material used in construction work
  supertype:  #building_material  material used for constructing buildings
  subtype:  #ashlar  a rectangular block of hewn stone used for building purposes
  subtype:  #cinder_block  a concrete building block made with cinder aggregate
  subtype:  #keystone__headstone  the central building block at the top of an arch or vault
     subtype:  #quoin__coign__coigne  the keystone of an arch
  subtype:  #voussoir  wedge-shaped stone building block used in constructing an arch or vault
  subtype:  kr#lego

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