The third step also involes building the steel skeleton. This steel frame has outer walls ( or curtain walls) the support almost all the weight of the building . The weight from all the floors gets transferred directly to the vertical columns. This sends forces through the steel skeleton down into the buildinding's base. In modern skycrapers, these exterior curtain walls are made almost entirely of gladd which gives more floor space for tenants to live or work . Once the skeleton has been built,