To eliminate the necessity for fabricating hollow extrusion dies for lower rails by block gate types.

This block gate for truck is configured by piling an upper rail, middle rail and lower rail 11 formed by a hollow extrusion die and joining one another with a through a bolt 9 and nut a 10. A hinge mounting plate 11C is formed on the bottom inside surface with a horizontal wall 11D. A lower cover 12 composed of a horizontal wall 12A and a vertical wall 12B is installed to the lower edge of the inside wall 11B of the lower rail 11 by fixing the upper end of the vertical wall to the lower edge of the inside wall. The ends of the horizontal wall 11D of this hinge mounting plate 11C and the horizontal wall 12A of the lower cover 12 are joined each other by recessed and projecting fitting, and installation structure for the lower rail 11 and the lower cover 12 is the same even if the type of the block gate is different.