What does it mean? "Clamped at start and end"

Hello everybody

As shown in the figure below,
What does the “clamped at start and end” sentence mean?

Please explain.

Hello - an open NURBs curve or one that has a kink or hard corner at the seam if it is closed has degree number of knots (‘fully multiple’) at each end if it is clamped - I think the only non-clamped curves you’ll run into in Rhino are periodic ones - these are closed curves and have an underlying structure that has degree number of control points extending beyond the seam in the curve - wrapping around in each direction - even though you don’t see that. So when you move the control point at the seam, the seam stays smooth - does not form a kink. As far as I know there is no situation in which you will encounter a Nurbs curve that is not clamped other than periodic curves in Rhino.

Make two closed curves with the curve command, one with Sharp=Yes. The first one will be periodic the other ‘clamped’.

-Pascal

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