--- a/+multiblock/DiffOp.m	Fri Dec 07 16:10:58 2018 +0100
+++ b/+multiblock/DiffOp.m	Mon Dec 10 08:29:41 2018 +0000
@@ -10,7 +10,7 @@
     end
 
     methods
-        function obj = DiffOp(doHand, g, order, doParam)
+        function obj = DiffOp(doHand, g, order, doParam, intfTypes)
             %  doHand -- may either be a function handle or a cell array of
             %            function handles for each grid. The function handle(s)
             %            should be on the form do = doHand(grid, order, ...)
@@ -24,14 +24,17 @@
             %            corresponding function handle as extra parameters:
             %            doHand(..., doParam{i}{:}) Otherwise doParam is sent as
             %            extra parameters to all doHand: doHand(..., doParam{:})
+            %
+            % intfTypes (optional) -- nBlocks x nBlocks cell array of types for
+            %                                 every interface.
             default_arg('doParam', [])
+            default_arg('intfTypes', cell(g.nBlocks(), g.nBlocks()) );
 
             [getHand, getParam] = parseInput(doHand, g, doParam);
 
+            obj.order = order;
             nBlocks = g.nBlocks();
 
-            obj.order = order;
-
             % Create the diffOps for each block
             obj.diffOps = cell(1, nBlocks);
             for i = 1:nBlocks
@@ -70,12 +73,11 @@
                         continue
                     end
 
-
-                    [ii, ij] = obj.diffOps{i}.interface(intf{1}, obj.diffOps{j}, intf{2});
+                    [ii, ij] = obj.diffOps{i}.interface(intf{1}, obj.diffOps{j}, intf{2}, intfTypes{i,j});
                     D{i,i} = D{i,i} + ii;
                     D{i,j} = D{i,j} + ij;
 
-                    [jj, ji] = obj.diffOps{j}.interface(intf{2}, obj.diffOps{i}, intf{1});
+                    [jj, ji] = obj.diffOps{j}.interface(intf{2}, obj.diffOps{i}, intf{1}, intfTypes{i,j});
                     D{j,j} = D{j,j} + jj;
                     D{j,i} = D{j,i} + ji;
                 end