Patent ID: 7793421

Claim:
A method of drawing an instrument across a curve in a surface for constructing an arch having first and second ends and a chord therebetween wherein the arch has an apex at a maximum height of the arch above the chord, the method comprising: providing a base member having a plurality of first indicators thereon and a slidable member having a plurality of second indicators thereon wherein said base member is adapted for slidable mounting of said slidable member thereon for relative sliding therebetween, and wherein said indicators reflect a range of characterizing arch dimensions, pivotably securing said base member to a surface through a pivot hole in a base end of said base member; selectively slidably locating said slidable member relative to said base member so as to align at least one of said second indicators on said slidable member with at least one of said first indicators on said base member according to corresponding dimensions characterizing said arch from said range; locating an instrument at a distal end of said sliding member; and rotating said base member and said slidable member about said pivot hole so as to draw said instrument across an arc having said corresponding dimensions, wherein said first indicators correspond to values representing the height of the arch above its corresponding chord and wherein said second indicators include values representing a distance between the first and second ends of the chord.