lower outermost edge an aris 31 in fig7 there are two blocks which are now referred to as 32 and 33 which replicate the block of the first embodiment and these are now shown one upon the other in a registered alignment where upwardly projecting portions such as 34 nest within correspondingly shaped cavities the two blocks have both upper and lower ariss at 35 and 36 and 37 which feature provides to some extent decorative as well as functional feature in minimising accidental chipping of the edge which could then be visually less preferred the two blocks in this case 32 and 33 are joined together by a building adhesive material an appropriate material for this purpose is a conventional cementitious adhesive in order to join the two bricks or blocks together a bead of the adhesive material is fed onto the respective meeting surfaces and the extent of this spread is such that when the two meeting surfaces come together the adhesive will be caused to spread substantially fully through all of the respective surfaces so as to provide not only an adhesion between the respective surfaces and therefore adhering the blocks together but also providing a sealing but as well against water ingress the amount of adhesive needed can be judged in practice and is chosen generally so that there is approximately a 2 millimetre separation gap between the meeting surfaces which is just enough to allow for an adhesive body of material and at the same time the dimensions of the respective mating surfaces are chosen to allow for this small separation the separation is chosen however so that in practice once the blocks are positioned they will.