The TERADOWEL or ULTRADOWEL Sleeves are installed into position on the timber formwork at specific intervals and at a height of half of the slab depth, before the formwork is installed and the slab is cast. The slab containing the sleeves is poured and, after the concrete has hardened sufficiently, the timber formwork is stripped. TERADOWELS or ULTRADOWELS are then inserted into the slots of the cast-in sleeves and the second pour is performed.