Arrangement for forming an elongate, channel-type accommodation space, comprising - at least two elongate mounting rail elements (1, 2), which have a substantially U-shaped cross-section, wherein two of the mounting rail elements (1, 2) 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 (1, 2), wherein the first shaped part is held in the two mounting rail elements (1, 2) via a form-locking connection, preferably via a latching connection, wherein the two shaped parts (4, 5) line the interior of the mounting rail elements (1, 2) created by the U-shape and the height of the accommodation space extends substantially over the entire height of the mounting rail elements (1, 2), wherein the mounting rail elements (1, 2) 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 (11, 12) 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 (43, 44) are formed at approximately half the height of the arm sections (41, 42). - at least two elongate mounting rail elements (1, 2), which have a substantially U-shaped cross-section, wherein two of the mounting rail elements (1, 2) 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 (1, 2), wherein the first shaped part is held in the two mounting rail elements (1, 2) via a form-locking connection, preferably via a latching connection, wherein the two shaped parts (4, 5) line the interior of the mounting rail elements (1, 2) created by the U-shape and the height of the accommodation space extends substantially over the entire height of the mounting rail elements (1, 2), wherein the mounting rail elements (1, 2) 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 (11, 12) 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 (43, 44) are formed at approximately half the height of the arm sections (41, 42).