Monorails, shipping containers and nuclear waste dumps are just some of the ways that US construction companies have interpreted Donald Trump’s call for an “impenetrable, physical, tall, powerful, beautiful wall” to march 2,000 miles across the country’s border with Mexico. Up to 400 bidding contractors were expected to submit their schemes this week to the US Customs and Border Protection agency, in a militarised beauty pageant worthy of one of Trump’s own reality TV shows.