It supports installing the arbitrary point of a simple curve and a clothoid curve This is an application for construction industry. When installing the arbitrary point on a central line in a simple curve or a clothoid curve, it is an application for computing a required element. In the case of a simple curve, the element for installing the arbitrary point on a central line from one point which exists on a central line is computed. In the case of a clothoid curve, the element for installing the arbitrary point on a central line from a B.T.C point is computed.