How to create a sketch on a split body?

[kthornbloom]

Hello, first post here. Can anyone help me understand this issue?

Here's a simplified example:
1 Create a box
2 Create a "Plane" type of "Form" intersecting it
3 Use "Split Body" and split your box in half with the plane. Turn off the top half of the box and the plane.
4 Now lets say you need to create a sketch on the lower half of the box, where it was cut. It's impossible to select that face for some reason.

[jeff_strater · Accepted solution]

The problem is in step 2:  "Create a "Plane" type of "Form" intersecting it".  Even if you don't modify the geometry at all, a "Plane" in the "Form" workspace is not really a plane - it will always be converted into a NURBS surface, which is not a viable surface to sketch on.  Instead, create a Work (Construction) Plane to split your design - this will create a planar surface that will allow you to sketch on it.