This a small version of the classic spline and whales design for drafting smooth contours. I made the Whales actually whales and magnetic for good holding power. (normally they are large lead weights). The design uses 15mm diameter magnets for the whales, and I am using an Ikea magnetic board for the drafting surface. The wire lines are just un-bent paper clips which fit in the whale's blowhole. They allow you to control particular points along the curve. Make sure the metal can rotate freely in the spline holes so that they can't apply a torque to the spline, only define an x,y position.

Contour away.