Lazer Cut Saddle Bridge Spreader
Works with 3mm plywood. I cut 4 pieces of the outside pieces and 6 for the inside.
You will need to use wood glue and a clamp for a construction. I'd recommend titebond 3 or something waterproof.
If you need to make the inside spacing larger for a thicker rope you will also need to extend the registration keys for the new overall width