OK-VISE Multi-Rail Packages . OK-VISE® Multi-Rail system is a simple way to build high precision modular fixtures. The Multi-Rail System adapts easily to various workpiece sizes, and the components of these systems can be reused and reconfigured quickly and easily for a variety of applications and workpieces. This means lower costs in fixtures and more flexibility in production! The system adapts to all possible workholding platforms like T-slot, blank, and grid platform. The size is selectable from three different categories: low, medium, and high.