#joist  beam used to support floors or roofs
  supertype:  #beam  long thick piece of wood or metal or concrete, etc., used in construction
  subtype:  #floor_joist__floorjoist  joist that supports a floor
  subtype:  #trimmer_joist__trimmerjoist__trimmer  joist that receives the end of a header in floor or roof framing in order to leave an opening for a staircase or chimney etc.

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