--- a/src/SbpOperators/SbpOperators.jl	Sun Nov 08 16:01:39 2020 +0100
+++ b/src/SbpOperators/SbpOperators.jl	Sun Nov 22 14:45:32 2020 +0100
@@ -14,5 +14,6 @@
 include("quadrature/quadrature.jl")
 include("quadrature/inverse_diagonal_inner_product.jl")
 include("quadrature/inverse_quadrature.jl")
+include("boundaryops/boundary_restriction.jl")
 
 end # module

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/SbpOperators/boundaryops/boundary_restriction.jl	Sun Nov 22 14:45:32 2020 +0100
@@ -0,0 +1,49 @@
+"""
+    BoundaryRestriction{T,N,R} <: TensorMapping{T,1,1}
+
+Implements the boundary operator `e` as a TensorMapping
+"""
+struct BoundaryRestriction{T,M,R<:Region} <: TensorMapping{T,1,1}
+    closureStencil::Stencil{T,M}
+    size::NTuple{1,Int}
+end
+export BoundaryRestriction
+
+
+function BoundaryRestriction(grid::EquidistantGrid{1,T}, closureStencil::Stencil{T,M},region::Region) where {T,M}
+    return BoundaryRestriction{T,M,typeof(region)}(closureStencil,size(grid))
+end
+
+LazyTensors.range_size(e::BoundaryRestriction) = (1,)
+LazyTensors.domain_size(e::BoundaryRestriction) = e.size
+
+" Restricts a grid function v on a grid of size (m,) to the scalar element v[1]"
+function LazyTensors.apply(e::BoundaryRestriction{T,M,Lower}, v::AbstractVector{T}, i) where {T,M}
+    # TODO: Currently closuresize = 4 for the stencil,
+    # but we should only be able to apply this for v[1] since the result is scalar.
+    @boundscheck if !(0 < Int(i) <= closuresize(e))
+        throw(BoundsError())
+    end
+    apply_stencil(e.closureStencil,v,Int(i))
+end
+
+" Restricts a grid function v on a grid of size (m,) to the scalar element v[m]"
+function LazyTensors.apply(e::BoundaryRestriction{T,M,Upper}, v::AbstractVector{T}, i) where {T,M}
+    # TODO: Currently closuresize = 4 for the stencil,
+    # but we should only be able to apply this for v[1] since the result is scalar.
+    @boundscheck if !(e.size[1] - closuresize(e) < Int(i) <= e.size[1])
+        throw(BoundsError())
+    end
+    apply_stencil_backwards(e.closureStencil,v,Int(i))
+end
+
+" Transpose of a restriction is an inflation or prolongation.
+  Inflates the scalar (1-element) vector to a vector of size of the grid"
+function LazyTensors.apply_transpose(e::BoundaryRestriction{T,M,Lower}, v::AbstractVector{T}, i) where {T,M}
+    @boundscheck if !(0 < Int(i) <= e.size[1])
+        throw(BoundsError())
+    end
+    return e.closureStencil[Int(i)-1]*v[1]
+end
+
+closuresize(e::BoundaryRestriction{T,M}) where {T,M} = M