that being approximately seven and five eighths inches 7 5 8 34 and a cross section in the appearance of an hourglass being two trapezoidal shapes attached together at the base of lesser dimension forming a back to back dovetail which will cause the furring element 3 to become entrapped within the dovetail shaped grooves 11 and 12 of the masonry element 1 and the insulating element 2 the furring element at its narrowest point shall be of adequate width to provide a reasonable zone of attachment for interior building fixtures and finishes one end of the furring element shall have cut into it a rectangular offset which shall act as a continuation of the excess mortar pocket 14 which is formed into the interior facing surface 7 of the masonry element said insulating element 2 shall be of a rigid self supporting material of uniform strength and density the thickness and actual formulation of this material shall vary depending upon the thermal and fire rating requirements for the service intended the overall length and width of the insulating element 2 shall be eight inches by sixteen inches 8 34 u00d7 16 34 exceeding the dimensions of the interior facing surface 7 of the masonry element 1 by three eighths of one inch 3 8 34 in each direction creating an offset 15 during.