Flat spline

[3] One can recreate an original draftsman's spline device with weights and a length of thin plastic or wood, flexible to bend enough without breaking.

Once adjusted to the satisfaction of the drafter, a line may be traced along the shaft, creating a template for a smooth curve.

[1][3] The Oxford English Dictionary finds the first recorded usage in the 18th century in East Anglia, England, and suggests the term spline may be related to splinter.

[5] By 1946, mathematicians had begun to devise mathematical formulae to serve a similar purpose,[6] and ultimately created efficient algorithms to find piecewise polynomial curves, also known as splines, that go smoothly through designated points.

Unlike a spline, the flexible curve does not have significant tension, so it maintains a given shape, instead of minimizing its curvature between point.