Hi!

I've been making a chassis for a car for the first time, and I've come to a point where I find it necessary to thicken my surfaces in order to progress further. The problem is that I get the error message "unable to thicken surfaces" when trying to do so, if anyone can see why and provide me with an answar or possibly a solution I would greatly appreciate it. The file is attached and if possible I would like all visible surfaces to be merged into one and further thickened.

Thanks in advance!