inside surfaces 33 or respective outside surfaces 34 is equal to the distance between first top notch 37 and second top notch 38 the reference to ground herein includes but is not limited to an assembly surface comprising soild grass a concrete slab a brick or stone pedestal etc a second pair of slab members 30 are positioned parallel to each other and spaced apart so as to allow each of the first and second bottom notches 39 and 40 to dovetail with the first and second top notches 37 and 38 of the first pair of slab members successive courses 21 may then be added with each such course having a primary pair of of slab members 30 and a secondary pair of slab members 30 which are assembled in like fashion to the first and second pairs of slab members 30 by dovetailing to the course immediately below which may at first be the bottom course 20 and thereafter may be one of the successive courses 21 although a successive course 21 of slab members for fire pit 13 as with bottom course 41 will consist of four slab members 30 the fire pit height can also be adjusted by utilizing only one half of a course which may be accomplished through the addition of only.