Freighthopping or trainhopping is the act of surreptitiously boarding and riding a freightcar, which is usually illegal.
Two hobos riding the rods
A freight train with freight hoppers in Mexico
Freight-hopping youth near Bakersfield, California (National Youth Administration, 1940)
A migrant worker is a person who migrates within a home country or outside it to pursue work. Migrant workers usually do not have an intention to stay permanently in the country or region in which they work.
Migrant workers in California, 1935
In Ghana, a migrant hawker carries colorful textiles on his head for sale
A Mingong working in China
Stranded migrant workers in India during COVID-19 lockdown