A system for mounting a side glazed unit of a means of transport, in particular a train glazed unit, in a peripheral opening, said system comprising a glazed unit and said glazed unit being a multiple, fixed, glazed unit having an outer face that faces an outer space and an inner face that faces an inner space, said outer face of the glazed unit being continuous in appearance with an outer flank of said opening over its entire periphery, said glazed unit comprising: - an outer glass pane having an outer face that faces the outer space, a peripheral edge and an intermediate face opposite the outer face, said outer glass pane preferably being laminated and thus comprising at least one outer glass sheet, one inner glass sheet, as well as a plastic material sheet located between said outer glass sheet and said inner glass sheet, each sheet (3, 4, 5) of said outer glass pane having a peripheral edge (30, 40, 50), - an inner glass pane having an inner face that faces the inner space, an intermediate face opposite the inner face, as well as a peripheral edge, - an internal structure that is located on the inner periphery of said outer glass pane and on the inner periphery of said inner glass pane, it being at least in part further toward the center than the peripheral edge (20, 60) respectively of said outer glass pane and said inner glass pane, and that holds together these two glass panes in such a way that the glazed unit provides a separation between said outer space and said inner space with a glazed unit cavity located between said glass panes (2, 6), said internal structure comprising a connecting cavity having a centripetal bottom and a centrifugal opening, characterized in that said opening comprises a lock that is fixed to said opening and is located more centrifugal than the edge of said inner glass pane, said lock having a side wing extending inside said connecting cavity and opposite an edge of said intermediate face of the inner glass pane by a 90° rotation of said side wing and in that an outer seal, preferably hollow, is located in a mounting space between, on the one hand, said outer flank and, on the other hand, the edge of said outer glass pane or, on the other hand, the edge of said outer glass sheet. - an outer glass pane having an outer face that faces the outer space, a peripheral edge and an intermediate face opposite the outer face, said outer glass pane preferably being laminated and thus comprising at least one outer glass sheet, one inner glass sheet, as well as a plastic material sheet located between said outer glass sheet and said inner glass sheet, each sheet (3, 4, 5) of said outer glass pane having a peripheral edge (30, 40, 50), - an inner glass pane having an inner face that faces the inner space, an intermediate face opposite the inner face, as well as a peripheral edge, - an internal structure that is located on the inner periphery of said outer glass pane and on the inner periphery of said inner glass pane, it being at least in part further toward the center than the peripheral edge (20, 60) respectively of said outer glass pane and said inner glass pane, and that holds together these two glass panes in such a way that the glazed unit provides a separation between said outer space and said inner space with a glazed unit cavity located between said glass panes (2, 6), said internal structure comprising a connecting cavity having a centripetal bottom and a centrifugal opening, characterized in that said opening comprises a lock that is fixed to said opening and is located more centrifugal than the edge of said inner glass pane, said lock having a side wing extending inside said connecting cavity and opposite an edge of said intermediate face of the inner glass pane by a 90° rotation of said side wing and in that an outer seal, preferably hollow, is located in a mounting space between, on the one hand, said outer flank and, on the other hand, the edge of said outer glass pane or, on the other hand, the edge of said outer glass sheet.