Abstract: The present invention relates to a structural element and more particularly to prefabricated T-beams which are designed to be manufactured in different dimensions and which are capable of supporting high loads. It is an object of the invention to provide such structural elements of great strength and which can be manufactured in dimensions necessitated by individual requirements with relatively overall low labor and material costs. According to the invention there is provided a prefabricated metal form characterized by the fact that it is disposed to form an arch shape between parallel support T-beams underneath the concrete flooring during the curing phase of the concrete construction, which is designed to take up the tension and stress of the above flooring, said form elements disposed in parallel in relation to one another.