An arris protection joint for edging the arrises of cured material pourable on opposite sides of the joint prior to curing of the said material, the joint comprising: • an opposed pair of elongate arris members (12,14) for edging the cured material, the arris members being: • complementarily formed along their length with a wave shape, with each member extending across a mid-plane of the joint from one side to the other and back again at successive positions along the length of the joint, whereby on pouring of the curable material it is formed into inter-digitated fingers edged by the arris members, which fingers extend through the depth of the material, corresponding to the width of the arris members, and the arris members having: • means for anchoring them in the respective poured material on opposite sides of the joint and • adaptations enabling their support in the cavity of a repair joint, or in a sub-base of a construction joint with their top at least substantially flush with the concrete slabs and • the arris members are of moulded polymeric material and characterised in that: • the arris members have integrally moulded spacers for holding them at a separation from each other which is small in comparison to the extent of the wave form and • supports complementary with the adaptations of the arris members for their support in the cavity. • an opposed pair of elongate arris members (12,14) for edging the cured material, the arris members being: • complementarily formed along their length with a wave shape, with each member extending across a mid-plane of the joint from one side to the other and back again at successive positions along the length of the joint, whereby on pouring of the curable material it is formed into inter-digitated fingers edged by the arris members, which fingers extend through the depth of the material, corresponding to the width of the arris members, and the arris members having: • means for anchoring them in the respective poured material on opposite sides of the joint and • adaptations enabling their support in the cavity of a repair joint, or in a sub-base of a construction joint with their top at least substantially flush with the concrete slabs and • the arris members are of moulded polymeric material and characterised in that: • the arris members have integrally moulded spacers for holding them at a separation from each other which is small in comparison to the extent of the wave form and • supports complementary with the adaptations of the arris members for their support in the cavity. • complementarily formed along their length with a wave shape, with each member extending across a mid-plane of the joint from one side to the other and back again at successive positions along the length of the joint, whereby on pouring of the curable material it is formed into inter-digitated fingers edged by the arris members, which fingers extend through the depth of the material, corresponding to the width of the arris members, and the arris members having: • means for anchoring them in the respective poured material on opposite sides of the joint and • adaptations enabling their support in the cavity of a repair joint, or in a sub-base of a construction joint with their top at least substantially flush with the concrete slabs and • the arris members are of moulded polymeric material and • means for anchoring them in the respective poured material on opposite sides of the joint and • adaptations enabling their support in the cavity of a repair joint, or in a sub-base of a construction joint with their top at least substantially flush with the concrete slabs and • the arris members are of moulded polymeric material and • the arris members have integrally moulded spacers for holding them at a separation from each other which is small in comparison to the extent of the wave form and • supports complementary with the adaptations of the arris members for their support in the cavity.