The old string method for tracing an ellipse is tried and true (see "Simple Interior Arches," 2/93). But for an exacting curve that won't get buried in drywall, the technique has its pitfalls. It's difficult to keep the pencil perfectly straight while holding constant tension on the string, and the pencil point runs with the grain of the wood. These snares result in an imperfect shape and wobbles along the curve, problems that Grant Taylor, a custom doormaker in South Ackworth, N.H., couldn't live with. He needs to cut very precise curves on a semi-production basis to fit custom glass panels, and the tastes of discerning clients. So Taylor fashioned a router jig. It takes some time to build this jig,
