I made this for my two year old neighbor’s birthday.
I drilled the holes in the trailer for the standard small crayons. It didn’t take long to realize that this was a mistake for a two year old, as he accidentally kept breaking off the crayons in the holes. I found some plastic mechanical crayons that proved to be a much better solution. I did have to re-drill all the holes out a little bit bigger, which wasn’t a problem.