I'm trying to create a lip/groove feature on a model that I've split into two solid bodies and placed into an assembly.

I've attached some photos of the preview once I've tried to create the lip/groove feature, it doesn't look like this when I'm clicking through the edges for the lip/groove.

I'll try to attach my model so you can get a closer look at the problem.

If anyone has any advice on this it would be greatly appreciated.

Oliver Sunderland - Product Design Student.