Here's one tailor-made for northern climates to keep out murderous beings invading into the civilized lands of the south. It can be called the ICE Wall...

As an added bonus we can man it with convicted felons especially those from Anifa, Black Lives Matter etc. It's very simple, offer them a choice: serve on the Wall or get castrated.
Every time I’ve driven into Canada the Canadian border guards pretty much ask for your entire life story before they let you through.