Simplify the following text for a Grade 8 native English-speaking person.
Original: The internal columns of the arcade with their attached shafts , the ribs of the vault and the flying buttresses , with their associated vertical buttresses jutting at right-angles to the building , created a stone skeleton .
Simplified: The columns of the inside , the ribs of the vault ( or roof ) and the flying buttresses , made a strong stone skeleton .