A yurt is a portable, bent dwelling structure traditionally used by nomads in the steppes of Central Asia. The structure comprises a crown or compression wheel usually steam bent, supported by roof ribs which are bent down at the end where they meet the lattice wall (again steam bent). The top of the wall is prevented from spreading by means of a tension band which opposes the force of the roof ribs. The structure is usually covered by layers of fabric and sheep's wool felt for insulation and weatherproofing.