--- a/src/Grids/EquidistantGrid.jl	Sun Feb 07 21:28:53 2021 +0100
+++ b/src/Grids/EquidistantGrid.jl	Mon Feb 08 18:43:38 2021 +0100
@@ -22,6 +22,13 @@
         end
         return new{Dim,T}(size, limit_lower, limit_upper)
     end
+
+	# Special constructor for 0-dimensional grids.
+	function EquidistantGrid(size::Tuple{}, limit_lower::Tuple{}, limit_upper::Tuple{})
+		#TODO: 	Need to specialize T.
+		#		Is Float64 a good choice here? How to propage from arguments?
+        return new{0,Float64}(size, limit_lower, limit_upper)
+    end
 end
 export EquidistantGrid
 
@@ -104,3 +111,21 @@
 """
 boundary_identifiers(g::EquidistantGrid) = (((ntuple(i->(CartesianBoundary{i,Lower}(),CartesianBoundary{i,Upper}()),dimension(g)))...)...,)
 export boundary_identifiers
+
+
+"""
+    boundary_grid(grid::EquidistantGrid,id::CartesianBoundary)
+	boundary_grid(::EquidistantGrid{1},::CartesianBoundary{1})
+
+Creates the lower-dimensional restriciton of `grid` spanned by the dimensions
+orthogonal to the boundary specified by `id`. The boundary grid of a 1-dimensional
+grid is a zero-dimensional grid.
+"""
+function boundary_grid(grid::EquidistantGrid,id::CartesianBoundary)
+    dims = collect(1:dimension(grid))
+    orth_dims = dims[dims .!= dim(id)]
+    return restrict(grid,orth_dims)
+end
+export boundary_grid
+boundary_grid(::EquidistantGrid{1},::CartesianBoundary{1}) = EquidistantGrid((),(),())
+boundary_grid(::EquidistantGrid{1},::CartesianBoundary) = throw(DimensionMismatch("dimension of Grid and BoundaryIdentifier not matching"))

--- a/test/testGrids.jl	Sun Feb 07 21:28:53 2021 +0100
+++ b/test/testGrids.jl	Mon Feb 08 18:43:38 2021 +0100
@@ -63,6 +63,36 @@
         @test boundary_identifiers(g) == bids
         @inferred boundary_identifiers(g)
     end
+
+    @testset "boundary_grid" begin
+            @testset "1D" begin
+                g = EquidistantGrid(5,0.0,2.0)
+                (id_l, id_r) = boundary_identifiers(g)
+                @test boundary_grid(g,id_l) == EquidistantGrid((),(),())
+                @test boundary_grid(g,id_r) == EquidistantGrid((),(),())
+
+            end
+            @testset "2D" begin
+                g = EquidistantGrid((5,3),(0.0,0.0),(1.0,3.0))
+                (id_w, id_e, id_s, id_n) = boundary_identifiers(g)
+                @test boundary_grid(g,id_w) == restrict(g,2)
+                @test boundary_grid(g,id_e) == restrict(g,2)
+                @test boundary_grid(g,id_s) == restrict(g,1)
+                @test boundary_grid(g,id_n) == restrict(g,1)
+            end
+            @testset "3D" begin
+                g = EquidistantGrid((2,5,3), (0.0,0.0,0.0), (2.0,1.0,3.0))
+                (id_w, id_e,
+                 id_s, id_n,
+                 id_t, id_b) = boundary_identifiers(g)
+                @test boundary_grid(g,id_w) == restrict(g,[2,3])
+                @test boundary_grid(g,id_e) == restrict(g,[2,3])
+                @test boundary_grid(g,id_s) == restrict(g,[1,3])
+                @test boundary_grid(g,id_n) == restrict(g,[1,3])
+                @test boundary_grid(g,id_t) == restrict(g,[1,2])
+                @test boundary_grid(g,id_b) == restrict(g,[1,2])
+            end
+    end
 end
 
 end