Cubby per-cell dividers landed exactly flush on the board below and under the board above — coplanar faces that shimmer and read as merged into the shelf. Extend each divider 1mm into both boards (centre unchanged) so it tucks under the top board and onto the bottom board with a solid, seam-free join. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>