Abstract: A repair structure for the repair, mainly, of leaking pipelines. The repair structure is a bandage of absorbent material impregnated with a curable resin. The bandage is wrapped round the pipeline to form a hard seal casing when the resin cures. The bandage preferably comprises also an impermeable membrane and a vent to allow leaking medium to escape while the bandage is being applied, with the membrane innermost, and while the resin is curing. The vent comprises a bush cast around a vent sleeve and bonded to the membrane. The resin which is used to form the vent bush and the membrane is the same as that used for the impregnation of the absorbent layer so that such layer will bond to the membrane. The sleeve is removable and can be replaced by a solid plug to seal the vent bush when the rigid seal casing is formed. The casing extends over a gallery in the region of the joint so that it will act as a bellow and accomodate large relative pipe section movements without failing.