Designed to provide a pre-set support system cast in concrete ceilings, walls, and floors to allow flexibility of attachment at any point along the channel, they provide an excellent support system for pipe, conduit, and cable trays. Continuous concrete. B-Line series concrete inserts include continuous concrete inserts, spot inserts, and more. Ceiling attachment / support Concrete inserts help support and attach trapeze hangers, suspended pipe racks, cable trays and single or multiple pipe hangers in ceilings. And with Unistrut's wide range of styles and accessories, there are more ways than ever to. Flex-Strut Concrete Inserts are the ideal solution for easily installed anchors to concrete foundations. It is also sometimes known as Cast-in Channel or P3270 Unistrut Concrete Insert Channel. It is made from Pre-galvanised 41x41x2.