If Trump were to put me in charge of the wall project, the wall would not be built at the border but within the 100 mile wide, constitution free, "border zone".

There would be plenty of US room on the "Mexican" side of the wall for police stations, access roads, etc. Most likely there would be whole US cities on the "Mexican" side.

If you are going to tunnel under "my wall" both ends of the tunnel will be in the US. My police officers will use seismographs to detect your tunneling and they can show up wherever you are and arrest you before you make much progress.

If you are going to vandalize or weaken my wall, my officers can arrest you and repair the damage whichever side you chose to attack.

If you throw rocks at the officers patrolling the wall, they can arrest you because you will necessarily have thrown them from US soil.

If you are going to scale my wall with a ladder, sensors will alert officers and they can arrest you before you get too far.

What would the purpose of the wall be?

If you are an undocumented migrant in El Paso and

• go to the Greyhound Station you are going to get picked up because my officers are waiting there and El Paso is in the Constitution free zone.
• same thing at the airport and train station
• drive through an approved wall crossing point you are going to get picked up because my officers are checking papers there
• same thing if you hitch hike, walk, or ride a bicycle
• if you stick around in El Paso then soon my officers will find you

I doubt Trump is picking me soon and I still oppose the wall. However, if the wall must stick close to the actual border it is ridiculously stupid because

• any wall built on a river bank is going into the sea
• any wall built within rockshot of territory not controlled by the US will be pelted with rocks until it collapses