An expendable article for forming the side edge of a poured in place concrete structure, the article comprising a fabricated, elongated hollow box having three interconnected sides that together define in cross section a triangular shape, including an hypotenuse side and a base side and having vertically aligned apertures in the said sides for receiving therethrough a retaining stake. The box end includes an inner periphery having a plurality of corners and defining a hole. Devices that allow for the input of location and pressure information may use embodiments of the invention, including computers with pressure sensitive mice or digitizer tablets, PDAs, or tablet computers. The new mathematical model may also adjust a control parameter where the control parameter may exist between two values. The helmet size can be not only partially decreased but also partially increased.