They can find ways to go over a fence and under it. The reason WHY they want to come here will not change with the fence.
"They can find ways to go over a fence and under it. The reason WHY they want to come here will not change with the fence."
No single thing will stop illegal immigration entirely (including a fence). But, a fence will make it much more difficult and reduce the number significantly.
Do you lock your doors and windows? Doing so won't stop a determined criminal, but it will deter the casual thief who is looking for an easy hit. Same principle applies here. Build a wall, and only the most determined ones will even attempt entry. The rest will see the wall and walk away.