Open borders are notoriously difficult to patrol, but walls seriously limit illegal crossings and make patrolling much easier, more effective. The combination is simply a must. This is why the US Border Patrol wants a wall.
The only ones who do not want a wall are those who do not really care about all illegal entry of drugs, of gangs, of thieves, of rapists, of murderers, of sex trafficking, of child prostitution, of criminal aliens who bilk the system by the billions--this especially includes Democrats, who know they will benefit politically from the displacement of current citizens.