is preferred that it be made in at least two pieces 22l and 22r this is because smaller refractory shapes are easier to form and are also easier to handle during installation obviously block 22 could be made of three or even more pieces if desired side faces 42 and 43 of block 22 converge towards the inner end as already described for block 21 it will be evident that the upper face 44 of block 22 will be formed with such an angle so that when block 22 is assembled with block 21 and the assembly placed in the furnace lower face 46 of block 22 will be parallel to upper face 25 of refractory lining brick 24 generally these faces 25 and 46 will be horizontal when the furnace is in its upright position in the case of a bof similarly upper wedge block 23 could be made as a single piece but is preferably made in two or more pieces pieces 23r and 23l of a pair which are mirror images of each other being shown in fig9 through 13 note that in fig9 and 10 block 23 is looked at from the outside of the furnace inward when block 23 is in place whereas fig6 and 7 look at block 22 from the inside of the furnace when the block is in place again the angle of upper face 48 of block 23 will be such that when assembled with block 21 upper face 48 is parallel to the horizontal surfaces 25 of lining brick 24 also side faces 49r and 49l of block 23 will be tapered inward in the same.