--- a/src/Grids/multiblockgrids.jl	Fri Apr 11 08:13:21 2025 +0200
+++ b/src/Grids/multiblockgrids.jl	Fri Apr 11 15:58:17 2025 +0200
@@ -1,4 +1,3 @@
-
 struct MultiBlockGrid{T,D,GT, CT} <: Grid{T,D}
     grids::GT
     connections::CT
@@ -15,9 +14,6 @@
 connections(g::MultiBlockGrid) = g.connections
 
 Base.getindex(g::MultiBlockGrid, I...) = g.grids[I...]
-# function boundary_identifiers end # Requires function from manifolds?
-# function boundary_grid end # Should return a MultiBlockGrid with the right connections?
-
 
 min_spacing(g::MultiBlockGrid) = minimum(min_spacing, grids(g))
 
@@ -38,13 +34,6 @@
 end
 
 
-# function boundary_indices end # Need to figure out the grid functions first?
-# function eval_on end # Need to figure out the grid functions first?
-# function Base.map end # Need to figure out the grid functions first? Should only have to implement the iterator interface
-
-# Plotting recipes
-
-
 """
     MultiBlockBoundary{N, BID} <: BoundaryIdentifier
 
@@ -65,6 +54,17 @@
 
 connection(t::Tuple) = connection(t...)
 
+# function boundary_identifiers end # Requires function from manifolds?
+
+function boundary_grid(g::MultiBlockGrid, bId::MultiBlockBoundary)
+    return boundary_grid(grids(g)[grid_id(bId)], boundary_id(bId))
+end
+
+# function boundary_indices end # Need to figure out the grid functions first?
+# function eval_on end # Need to figure out the grid functions first?
+# function Base.map end # Need to figure out the grid functions first? Should only have to implement the iterator interface
+
+# Plotting recipes
 
 
 # Nested indices??

--- a/test/Grids/multiblockgrids_test.jl	Fri Apr 11 08:13:21 2025 +0200
+++ b/test/Grids/multiblockgrids_test.jl	Fri Apr 11 15:58:17 2025 +0200
@@ -120,7 +120,17 @@
     end
 
     @testset "boundary_grid" begin
-        @test_broken false
+        g1 = MultiBlockGrid(multiblockgrid1d()...)
+        @test boundary_grid(g1, MultiBlockBoundary{1,LowerBoundary}()) == ZeroDimGrid(0.)
+        @test boundary_grid(g1, MultiBlockBoundary{3,UpperBoundary}()) == ZeroDimGrid(3.)
+
+        g2 = MultiBlockGrid(multiblockgrid2d()...)
+        b1lb = MultiBlockBoundary{1,CartesianBoundary{1,LowerBoundary}}()
+        @test boundary_grid(g2, b1lb) == TensorGrid(ZeroDimGrid(0.),equidistant_grid(0,1,5))
+
+        gm = MultiBlockGrid(multiblockgrid_matrix()...)
+        b21lb = MultiBlockBoundary{CartesianIndex(2,1),CartesianBoundary{2,LowerBoundary}}()
+        @test boundary_grid(gm, b21lb) == TensorGrid(equidistant_grid(1,2,11),ZeroDimGrid(0.))
     end
 
     @testset "min_spacing" begin