Fontanot - Outdoor Spiral Staircase. The Klio Zink outdoor staircases have pressed steel treads with embossed holes to make them non-slip and to drain off rainwater. The spacers between the treads allow varying the rise measurement so that the staircase is adaptable to any home. The railing of the outdoor staircase is formed by steel balusters with the handrail in black PVC. All the metal components are hot-dip-galvanised and the nuts and bolts are in stainless steel.