a rectilinear body having a front plate and a structurally interconnected back plate,

the back plate defining a V notch having a fixed angle formed by two converging linear sides that intersect at an apex for simultaneously contacting a first point and a second point along the circumference of the circular curve, and an angulated through slot having one end portion proximate to the apex and an opposing end portion distal from the apex, and

the front plate defining a cut out area exposing the V notch and defining an elongated rectilinear notch having one end portion communicating with one linear side of the V notch, an opposing base end portion distal from the V notch, an upper edge and a spaced apart parallel wedge track, the upper edge and the wedge track angulated relative to a bisector of the V notch other than perpendicularly;

a wedge having a base end portion, an opposing tapered end portion, an upper measuring edge portion and a track edge portion, the wedge movable along the wedge track on the track portion and across the bisector so that the measuring edge portion contacts the circumference of the circular curve between the first and second points;

measuring indicia on the body to determine travel distance of the wedge along the wedge track; and

distance of positional change of the wedge along the wedge track correlates to the radius of the circular curve.