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 .