Abstract: The rig mat is laid on a substrate to provide a surface to bear and distribute weight over the substrate. The rig mat call be used individually or juxtaposed in an assembly of mats to provide the bearing surface. The rig mat has a top plate and a bottom plate disposed in parallel alignment. A spacer grate is sandwiched between and fixed to the plates. An edge binder is disposed around the perimeter edges of the plates to bind them together and to enclose the spacer grate within the space between the plates. The spacer grate is made up of a number of grating bars disposed in a parallel to each other. Cross-rods disposed in parallel to each other and perpendicular to the grating bars pass through and attach to the grating bars to fix the spacing between the grating bars.