Construction of 3D Objects
Grade 3 geometry shifts from identifying 3D shapes to constructing them. A net is a 3D shape unfolded flat: seeing a cube's net and folding it back up reveals that a cube has 6 square faces, 12 edges, and 8 vertices. A skeleton uses straws and connectors to show the edges and vertices without the faces. Both construction methods force students to internalize the properties of each shape, not just recognize it by appearance.
Faces, edges, and vertices
Face: a flat surface. Edge: where two faces meet. Vertex: where three or more edges meet. A cube: 6 faces (all squares), 12 edges, 8 vertices. A triangular prism: 5 faces (2 triangles + 3 rectangles), 9 edges, 6 vertices. These counts are not arbitrary: Euler's formula F + V = E + 2 relates them for any convex polyhedron, though Grade 3 students discover this empirically rather than formally.
Nets and skeletons
A net is the 2D template that folds into a 3D object. Drawing and cutting a cube's net (a cross of 6 squares) then folding it creates the cube. Students must visualize which faces will be where after folding: spatial reasoning at its most demanding. A skeleton uses straws for edges and clay or connectors for vertices: it shows the structure without the surfaces.
Cultural 3D objects
The BC curriculum specifically mentions jingle dress bells (cone-shaped), bentwood boxes (rectangular prism with curved wood), birch bark baskets (cone or cylinder), and pithouses (cone/cylinder combination on a rectangular base). Each is a real-world application of 3D geometry knowledge. Discussing why these shapes were chosen for their cultural and practical purposes connects geometry to Indigenous design thinking.