A raccoon was reaching into our milk crate nesting boxes and killing/hurting our chickens- the raccoons could reach through the handle holes but not the grid on the sides, so I made these plugs. I made them to fit all the milk crate types we had on hand and they're a good general fit rather than being glove like for any of them.
We use the milk crate nesting boxes as a part of Justin Rhodes' ‘ChickShaw’ (no affiliation, just a fan).
These use an M3 screw and nut to secure them- I've not needed threadlocker but it may be a good idea.
The Sunlu PLA+ I printed these in has held up well in the Texas sun and heat, there are no signs of wear or fading after 6 months.