Each number has 2 fixing holes for 3mm(1/8") fixing screws.
The best results, I find, are printing with ASA - UV resistant - can withstand temps up to 95C - easy to print (as long as you have an enclosure).
PETG would have to be my 2nd choice, but for most climates should be OK, I think.
The author marked this model as their own original creation.