Cross halving join — mark half-lap regions where boards cross

What does this tool do?

Cross halving join creates marker faces for half-lap regions where two boards cross at a right angle — for example a vertical divider passing through a horizontal shelf. Each mark is a flat face in its own group (default ABF_CrossHalvingJoin, on the layer of the same name) so the CNC can cut half the thickness off each board and the two boards lap into a cross.

Use it when you need to:

• Join shelves and dividers with cross half-laps in cabinets, shelving and grid frames.
• Mark many crossings at once: one click creates the mark on the clicked board and on every board perpendicular to it.
• Adjust the offset (clearance) and end stretch (tool relief) in millimetres before creating.

Basic steps

1. Select at least two crossing board groups/components. (With an empty selection the tool takes every top-level group in the model.)
2. Click the Cross halving join icon. The tool isolates those boards and turns on X-ray and color-by-tag so the crossing is easy to read.
3. Hover over a board's large face, near the edge on the side you want to lap. A cyan preview appears: the board's outline slides toward that edge by half its size — meaning the half nearest the edge you point at is the half that gets lapped.
4. Click to create the marks. The tool places lap faces on the clicked board and on every perpendicular board crossing it, clipped to each board's own outline, expanded by the offset and end stretch.

Repeat on other faces/edges as needed. Esc exits; the display mode returns to normal. Each click is one Undo step.

Adjusting parameters on the HUD

Three chips in the top-left corner — click a chip to type a new value:

• Tag — the group/layer name for the marks, default ABF_CrossHalvingJoin.
• Offset — extra clearance around the lap region, default 0.1 mm (so the two boards slip together more easily).
• Stretch — extra length at both ends of the slot, default 3 mm, so the round cutter clears the slot corners.

Keyboard

• Click – create the lap marks under the preview.
• Esc – exit the tool.

Common problems

• "Select at least two boards" message: the selection has fewer than two valid board groups/components (missing the parallel front/back face pair). Fix the board shape or select two boards.
• No preview: the cursor is not over a board's large face, or the board is not in the working set. Hover the middle of the face first, then move toward an edge.
• Click creates nothing: the clicked board has no perpendicular board crossing it in the working set — marks only appear between boards at right angles.
• Overlap warning: the new lap region touches existing sub-groups inside the board (labels, old lap marks). Delete the old marks or move the position and create again.
• Wrong half lapped: the lapped half is the one nearest the edge you point at. Undo and point near the opposite edge to flip sides.