This is my first post ever. I've been having a bit of trouble with the wheel wells on my prototype car body design. I have the full outer body surfaced, but I need to add in some firewalls to keep the driver separated from the wheels. To do this, I created a planar surface through the body, mirrored that surface, and then used "trim surface", selecting "mutual" and the three surfaces (car, and 2 planar surfaces). I selected the inner pieces to keep. However, the "mutual" option did not knit the surfaces together, and when I try to do a manual "knit surface", an error message pops up saying there are no edges to knit. That doesn't make sense because I used the body to cut the planar surfaces, so they should be exactly touching. Am I missing a step or something?