the flanks are identified in the sheet metal development these compression plates are the plates on which the bolt exerts the clamping force in compression and transmits its stress both to the base and to the flanks at least two regions of the surface thereof such that they are supported on the edges of either flank respectively in order to withstand compressive stresses between the compression plates and a hole configured for allowing the passage of a compression element such as a bolt or clamping screw contact between said plates and the flanks is established after the bend of the compression plates the way of contacting is by means of two regions of the surface thereof two regions which are located on the inner face of said compression plates after the bend which are supported on the edges of either flank respectively the compression of the clamping bolt is transmitted to the prismatic body to the base through the bend line connecting the compression plate and the base and to the flanks through the support regions either compression plate has a hole that allows the passage of the bolt through the inside of the prismatic body and with the support elements thereof the head.