are packed with spacers such as indicated for example at 420 at 422 424 and 426 these thusly nested panels or modules may be readily tranported with economy of space and free from damage to the site at which installation is to be made to be certain that appropriate glazing bar sections will be connected to one another in accordance with their unitary manufacture the matched glazing bar section may be provided with a coding representation a color coding is indicated by way of example in fig1 at c1 and c2 this coding may take the form of appropriate color printing on the matching sections so that matching sections may be readily identified and put into cooperating relationship from the above it will be seen that the method of the invention comprises forming a greenhouse structure of prefabricated modules which are interconnected through the intermediary of glazing bars which support glazing in the modules and which are formed of sections which are first connected to the respective modules and are then connected to each other in matching pairs to form the glazing bars the glazing bar sections which are to be connected together may be matched by bending the same together and are formed preferably as mirror image sections which are bent in juxtaposition with the same bending force in the same bending die the sections are formed to define cooperatively a longitudinally extending interior chamber in which is mounted a tubular member to which the sections are fastened the modules are aligned by mounting the same in a common ridge bar and base sill which are appropriately positioned more particularly the ridge bar of.