To provide a mechanism and a system capable of conveying a concrete secondary product to an installation plate, shortening the time before installation is completed, and carrying out the installation work even in a place in which no temporary road can be installed.

A traveling guide groove having an upwardly opened, U-shaped section comprises a traveling face formed in a center of the traveling face along the traveling direction, four conveying wheel bodies arranged on the traveling face at apexes of a square, a caster in contact with a traveling guide bottom so that wheels are rolled on the traveling guide bottom, a guide rotating body which is arranged in the traveling guide rotatably around a vertical shaft fixed to an upper portion of the caster, and a meandering preventive connection bar which is fixed to an upper portion of the vertical shaft and connected to a pair of right and left conveying wheel bodies, and further comprises guide tools respectively arranged before and behind the four conveying wheel bodies, a guide tool connection body to connect the front and rear guide tools to each other, and a front-rear holding bodies to connect the conveying wheel bodies in the right-to-left direction and the longitudinal direction.