Cords are extruded as open-ended billets of circular cross-section (like an O-ring). The cord achieves its sealing effect by the deformation of its cross-section once installed, on being compressed within the installation housing. Under operational conditions, the pressure exerted by the medium reinforces the sealing function.
The primary application for cords is as the basic material for joined O-rings. They are similar to the O-ring in the way they are handled and applied. They are used as static seals, e.g. for sealing larger pipe unions and as cover seals in container construction. Cords are frequently used for on-site repairs, being joined together to provide the "customized" dimensions. The process of end-joining cords to form a joined O-ring can be undertaken using cyano-acrylate or 2-component adhesives. However, for applications in seawater or other more demanding applications, bonding by means of an end-vulcanisation process is required.