This is the informal border crossing between Mexico and Guatemala near Ciudad Hidalgo, Mexico. People cross from Guatemala to Mexico to buy inexpensive products because of favorable exchange rates They then return to Guatemala. This trade is condoned by both countries and even though there are checkpoints nearby neither country has an interest in stopping this traffic.
It is only when people fleeing from Guatemala to Mexico move inland that they are stopped at Mexico checkpoints and detained or sent back home. This process of inland checkpoints and detention is known as the “vertical border.” It is designed to prevent migration to the United States long before the migrants reach the northern border of Mexico.