Specify continuity on a Square or Rail surface

Modeling > Create geometry > Build primary surfaces that maintain continuity >

In the option window of the tool you used to create a surface, use the pop-up menus next to the names of the generation and rail curves to choose what level of continuity the surface should maintain with its neighbor along that edge.

Set a manual tangent angle along an edge

In the option window, set the continuity for the edge to Tangent Angle.
Use the tangent angle manipulator to set the angle.

How do I use the tangent angle manipulator?

Click an axis line to set the tangent angle to 0, 90, 180, or 270 degrees.
Click an arc, then drag left and right to change the angle value, or type a number to set the value exactly.
When you are finished, click Go.

What if...?

I can’t achieve the continuity I want?

Make sure you clicked an edge or isoparametric curve of the adjacent surface when you used the Rail surface tool, not a left over free curve you used to create the surface.
Turn on the Rebuild check box for the edge. This allows the tool to change the geometry of the edge as it attempts to achieve continuity.
Turn on the Explicit control option, then increase how many spans the surface may have. This allows the Rail Surface tool to add more spans to the surface to achieve better continuity.

Certain types of continuity are not available in the pop-up menu for an edge?

Some continuity types (Tangent, Tangent Angle, Curvature) are only available on edges that are connected to surfaces.

If it looks like your new surface shares an edge with an existing surface, but the continuity choices are not available, it probably means you accidentally clicked a construction curve, not the edge of the existing surface.

To fix this, delete your new surface, then hide any construction curves that are “in the way” and re-create the surface.

I want to change the continuity of a surface after I’ve worked on other objects?

See View and edit the construction history of an object