diff --git a/nhf/build.py b/nhf/build.py
index 106577c..3e6ece3 100644
--- a/nhf/build.py
+++ b/nhf/build.py
@@ -90,7 +90,7 @@ class Target:
                 x = (
                     Cq.Workplane()
                     .add(x._faces)
-                    .add(x._wires)
+                    .add(x.wires)
                     .add(x._edges)
                 )
             assert isinstance(x, Cq.Workplane)
@@ -214,7 +214,7 @@ class Submodel:
     def write_to(self, obj, path: str):
         x = self._method(obj)
         assert isinstance(x, Model), f"Unexpected type: {type(x)}"
-        x.build_all(path)
+        x.build_all(path, prefix=False)
 
     @classmethod
     def methods(cls, subject):
@@ -271,11 +271,17 @@ class Model:
             total += 1
         return total
 
-    def build_all(self, output_dir: Union[Path, str] = "build", verbose=1):
+    def build_all(
+            self,
+            output_dir: Union[Path, str] = "build",
+            prefix: bool = True,
+            verbose=1):
         """
         Build all targets in this model and write the results to file
         """
         output_dir = Path(output_dir)
+        if prefix:
+            output_dir = output_dir / self.name
         targets = Target.methods(self)
         for t in targets.values():
             file_name = t.file_name
diff --git a/nhf/tool/__init__.py b/nhf/tool/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/nhf/tool/light_panel.py b/nhf/tool/light_panel.py
new file mode 100644
index 0000000..44c7920
--- /dev/null
+++ b/nhf/tool/light_panel.py
@@ -0,0 +1,121 @@
+from dataclasses import dataclass
+import cadquery as Cq
+from nhf import Material, Role
+from nhf.build import Model, target, assembly, TargetKind, submodel
+from nhf.parts.box import MountingBox, Hole
+from nhf.parts.electronics import ArduinoUnoR3
+import nhf.utils
+
+@dataclass
+class LightPanel(Model):
+
+    # Dimensions of the base panel
+    length: float = 300.0
+    width: float = 200.0
+
+    grid_height: float = 30.0
+    grid_top_height: float = 5.0
+    # Distance from grid to edge
+    grid_margin: float = 20.0
+    # Number of holes in each row of the grid
+    grid_holes: int = 9
+    grid_layers: int = 6
+    grid_hole_width: float = 15.0
+
+    base_thickness: float = 25.4/16
+    grid_thickness: float = 25.4/4
+    base_material: Material = Material.WOOD_BIRCH
+    grid_material: Material = Material.ACRYLIC_TRANSPARENT
+
+    controller: ArduinoUnoR3 = ArduinoUnoR3()
+
+    def __post_init__(self):
+        assert self.grid_holes >= 2
+        super().__init__(name="light-panel")
+
+    @target(name="grid", kind=TargetKind.DXF)
+    def grid_profile(self):
+        w = self.length - self.grid_margin * 2
+        h = self.grid_height + self.grid_top_height
+
+        # The width of one hole (w0) satisfies
+        # n * w0 + (n+1) t = w
+        # where t is the thickness of the edge
+        n = self.grid_holes
+        w0 = self.grid_hole_width
+        t = (w - n * w0) / (n + 1)
+        # The spacing is such that the first and last holes are a distance `margin`
+        # away from the edges, so it satisfies
+        # t + w0/2 + (n-1) * s + w0/2 + t = w
+        step = (w - t*2 - w0) / (n - 1)
+        return (
+            Cq.Sketch()
+            .push([(0, h/2)])
+            .rect(w, h)
+            .push([
+                (i * step + t + w0/2 - w/2, self.grid_height/2)
+                for i in range(0, n)
+            ])
+            .rect(w0, self.grid_height, mode='s')
+        )
+
+    def grid(self) -> Cq.Workplane:
+        return (
+            Cq.Workplane('XY')
+            .placeSketch(self.grid_profile())
+            .extrude(self.grid_thickness)
+        )
+
+    @submodel(name="base")
+    def base(self) -> MountingBox:
+        xshift = self.length / 2 - self.controller.length - self.grid_margin / 2
+        yshift = self.grid_margin / 2
+        holes = [
+            Hole(
+                x=x + xshift, y=y + yshift,
+                diam=self.controller.hole_diam,
+                tag=f"controller_conn{i}",
+            )
+            for i, (x, y) in enumerate(self.controller.holes)
+        ]
+        return MountingBox(
+            holes=holes,
+            hole_diam=self.controller.hole_diam,
+            length=self.length,
+            width=self.width,
+            centred=(True, False),
+            thickness=self.base_thickness,
+        )
+
+    def assembly(self) -> Cq.Assembly:
+        assembly = (
+            Cq.Assembly()
+            .addS(
+                self.base().generate(),
+                name="base",
+                role=Role.STRUCTURE,
+                material=self.base_material,
+            )
+        )
+        # Grid thickness t is fixed, so the spacing of the grid satisfies
+        # margin + t + (n-1) * spacing + margin = width
+        spacing = (self.width - 2 * self.grid_margin - self.grid_thickness) / (self.grid_layers - 1)
+        shift = self.grid_margin + self.grid_thickness / 2
+        for i in range(self.grid_layers):
+            assembly = assembly.addS(
+                self.grid(),
+                name=f"grid_{i}",
+                role=Role.STRUCTURE,
+                material=self.grid_material,
+                loc=Cq.Location(0, spacing * i + shift, self.base_thickness, 90, 0, 0),
+            )
+        return assembly
+
+
+if __name__ == '__main__':
+    import sys
+
+    p = LightPanel()
+    if len(sys.argv) == 1:
+        p.build_all()
+        sys.exit(0)