Open frame fixture designs allow welders full access inside the weldment without having to crawl on a solid worksurface.  The U-form spacer blocks which make up the base table, come in a variety of lengths (2’ up to 14’) and can be joined together with precision clamping and locating bolts generating 6,000 lbs holding force each.  A calibration laser can be used while adjusting the leveling pads for a perfectly flat base surface.