Abstract: A load displacement apparatus to displace a mobile platform along a structure includes a worm screw mounted on the platform for rotation about its axis that meshes with a plurality of support blocks mounted on the structure. The support blocks are spaced apart from one another along the structure to be successively engaged by the worm screw. Each support block includes a plurality of bearing balls freely movably supported and retained therein to selectively and movably engage the worm screw over at least an arc segment thereof such that the worm screw is always in meshing engagement with at least one of the support blocks. A scaffolding system incorporating the apparatus is also described.