It occurs to me that U-bolts exist, and if not, then threaded rod exists, which could be formed into u-bolts with a harbor freight bender. Seriously, you could likely turn a wall into a ladder in twenty minutes, with some power tools and preparation, well and a rope ladder to get down.
One could argue that you shouldn't give ideas, but heck, if I can think of it as a random thought, so can everyone else. No wall is going to keep out the truly determined. Most of the drugs come through legal entry anyway. Employers need to use E-Verify. It's not complicated.
Basically we are going through insane, expensive, and cruel methods, when just holding employers responsible, if we want to stop illegal immigration, would mostly handle it.