work VERY well.
https://www.conservativereview.com/commentary/2017/01/border-fences-work
Congress passed a bill in 1996 to require construction of a double-layered fence (triple-layer in some places) in the San Diego corridor along the coast. You can see a picture of the fence with razor wire here. By the end of the decade, apprehensions fell by 95% as illegals moved eastward, even though the fence covered only 14 miles of the 60-mile sector. The majority of this border sector, unlike most other areas of the border, also has a tall and solid single-layer fence. While nothing is foolproof, fences clearly work and take much of the pressure off the border patrol to keep up with the flow......
....The Yuma sector contains most of the remaining double-layer fencing with razor wire, including areas with triple layers and a 75-foot “no man’s land.” Not surprisingly, it has worked. Apprehensions have declined 96% since 2005 — falling from 138,438 to 5,902 in fiscal year 2014. And again, the double-layer fencing in Yuma and San Diego only cover a fraction of the sector. But they also have other areas with solid single-layered fencing. The other border sectors containing a sizable amount of effective single-layer fencing are El Centro and El Paso, and they have seen a dramatic decline in border crossings as well, although they are not as locked down as Yuma.