grooved cuboid 3d model

Create an exact CAD-style 3D model in millimeters. Base: a solid cuboid of 7.74 × 7.74 × 3.12 mm. Each of the 4 vertical side faces (7.74 × 3.12 mm) contains a centered horizontal groove: 0.72 mm wide, 0.72 mm deep, running the full 7.74 mm length, centered at mid-height (1.56 mm from top/bottom). On each face, add a second groove: same dimensions (0.72 × 0.72 mm), vertical, centered horizontally, running full height (3.12 mm). This vertical groove intersects the horizontal groove at the exact center, forming a cross. All grooves are precise boolean cuts, fully symmetric, with sharp edges and no fillets. Output a clean, watertight solid model.