The Great Wall of china did not work. It was incomplete. Couple hun miles of wall here then a big gap,some wall ,gap etc etc. our wall will not work either unless we ACTIVELY ENFORCE and patrol said wall. The biggest problem with our border issue is that there is basically no repercussions for breaching it. Round them up,give some food water and med treatment and ship them back. That's what we do. 2 weeks later they're back. Odds are sooner or later they'll make it. And they will. ENFORCE and protect. That is the answer