Dear all, I want to enforce DirichletBCs on an extruded mesh. For a normal unit cube tetrahedron mesh I could use the following face ID's: 1: x ==0 2: x==1 3: y==0 4: y==1 5: z==0 6: z==1 However, when I do the following: meshbase = RectangleMesh(Nx, Ny, Lx, Ly, quadrilateral=True) mesh = ExtrudedMesh(meshbase, Nz, Dz) I get this error: Traceback (most recent call last): File "VMS_patch_test_3D_Double_firedrake.py", line 51, in <module> FrontBackBC1 = DirichletBC(wSpace.sub(0).sub(1),Constant(0.0),(3,4)) File "/data/Software/firedrake/src/firedrake/firedrake/bcs.py", line 68, in __init__ raise NotImplementedError("Indexed VFS bcs not implemented on extruded meshes") NotImplementedError: Indexed VFS bcs not implemented on extruded meshes What should I do to properly identify my boundary faces? Regards, Hanie