I pinned this Montessori Nuts and Bolts Board to try as a DIY project to have in our classroom. We are brainstorming an outdoor woodworking space, but in the meantime, this would make a great addition.
I think you could also have multiple pipe cleaners coming from one number and students have to show multiple ways to add numbers to get to that number. Counting with pipe cleaners and beads. Great for fine motor development too.