Arrangement for forming an elongate, channel-type accommodation space, comprising - at least two elongate mounting rail elements , which have a substantially U-shaped cross-section, wherein two of the mounting rail elements are arranged such that their front faces abut via a joint , - a first shaped part and - a second shaped part , which is connected to the first shaped part for forming the channel-type accommodation space that extends at least substantially over the length of the two mounting rail elements , wherein the first shaped part is held in the two mounting rail elements via a form-locking connection, preferably via a latching connection (R), wherein the two shaped parts line the interior of the mounting rail elements created by the U-shape and the height of the accommodation space extends substantially over the entire height of the mounting rail elements , wherein the mounting rail elements have a substantially U-shaped cross-section, so that a first U-leg , a second U-leg and a connecting leg connecting the two U-legs with one another are formed, wherein the first shaped part has a floor section , a first arm section adjoining a first side of the floor section and a second arm section adjoining the opposite second side, wherein the configuration is such that the floor section rests against the connecting leg , the first arm section surrounds the free end section of the first U-leg and the second arm section surrounds the free end section of the second U-leg , and wherein the form-locking connection is created, on the one hand, between a first inwardly projecting projection formed on the first U-leg and a first latching profile formed on the first arm section and, on the other hand, between a second inwardly projecting projection formed on the second U-leg and a second latching profile formed on the second arm section , wherein the latching profiles are formed at approximately half the height of the arm sections . - at least two elongate mounting rail elements , which have a substantially U-shaped cross-section, wherein two of the mounting rail elements are arranged such that their front faces abut via a joint , - a first shaped part and - a second shaped part , which is connected to the first shaped part for forming the channel-type accommodation space that extends at least substantially over the length of the two mounting rail elements , wherein the first shaped part is held in the two mounting rail elements via a form-locking connection, preferably via a latching connection (R), wherein the two shaped parts line the interior of the mounting rail elements created by the U-shape and the height of the accommodation space extends substantially over the entire height of the mounting rail elements , wherein the mounting rail elements have a substantially U-shaped cross-section, so that a first U-leg , a second U-leg and a connecting leg connecting the two U-legs with one another are formed, wherein the first shaped part has a floor section , a first arm section adjoining a first side of the floor section and a second arm section adjoining the opposite second side, wherein the configuration is such that the floor section rests against the connecting leg , the first arm section surrounds the free end section of the first U-leg and the second arm section surrounds the free end section of the second U-leg , and wherein the form-locking connection is created, on the one hand, between a first inwardly projecting projection formed on the first U-leg and a first latching profile formed on the first arm section and, on the other hand, between a second inwardly projecting projection formed on the second U-leg and a second latching profile formed on the second arm section , wherein the latching profiles are formed at approximately half the height of the arm sections . <EOS>