In chat today, Aly's compile was failing, saying that there was a func_detailed displacement. It can be a tricky error to solve, since it reports a brush number that Hammer doesn't recognise. And the problematic displacement will not be in the displacements auto visgroup, only in the func_detail auto visgroup. So here's how to fix it if you can't find the offending brush: Turn off "Disp mask solid" Go to the Auto visgroups, untick everything, then tick Func Detail. Select all (Ctrl+A), then go to the Face Edit tool Select the Displacement tab, then click Destroy. The only drawback here is that if the displacement was one you'd spent time and effort on, it'll now be back to a flat brush.