Make an object open or closed

Converts an object between being open (having free endpoints or edges) and being closed (having connected endpoints/edges).

When a curve is closed, it forms a continuous loop, with no loose ends. When a curve is open it has two ends that can be moved independently, though they might happen to occupy the same point in space.

Similarly, a surface can be closed (periodic) across U, V, or both dimensions. When a surface is open, it has free edges.

Open or close a curve

Choose Object Edit > Close.
Click the curve.

Open or close a surface

Choose Object Edit > Close.
Click a U or V isoparametric curve or edge to open or close the surface across that dimension.

Close a curve or surface by attaching its ends/edges

Choose Object Edit > Attach > Attach.
Click the two ends of a curve, or click opposite edges of a surface.
Note
You must have at least four spans (not counting multi-knots) between the opposite edges of the surface to attach them.

What if...?

I want to know if an object is open or closed?

1. Pick the object.

2. Choose Windows > Information > Information Window.

3. The Geometry info section tells whether the object is open or closed.