More than 150 lorry drivers have staged a protest at the Irish border in a bid to highlight the importance of free-flowing movement.
A convoy of trucks made their way from Donegal and crossed the border into Co Derry.
Truck drivers taking part said they want to show how the free movement of freight is vital to businesses and trade.
The protest was brought to a standstill at the main border route, as hundreds of drivers and their supporters turned out to "show the world" what custom checks and infrastructure would look like.
There are about 13,800 border crossings every day between the Republic and Northern Ireland.
George Mills, from the Irish Road Haulage Association, said: "We don't have to fill out any documentation or electronics or otherwise to cross this border, which we need to do every day of the week because of where we live.
"We can't go anywhere without crossing the border, even to do our business with Dublin.
"After Brexit we will be crossing an EU/non-EU frontier and that's going to create so many problems.
"We want to show the world how easy it is now.
"The people of the UK don't seem to regard the border as important.
"Only 2% of their trade crosses this border, but it's nearly 100% of our trade that has to cross this border, so it's a big concern to us.
"We don't want to go back to any form of regulation that impacts that form of free movement of traffic.
"Our nearest port is Derry and Belfast, and they must bring up all our oil, coal, gas, animal feed, timber, coal.
"The nearest alternative is 200 miles away in Co Limerck that can handle that amount of cargo.
"If a ship load of coal comes into Derry and it's bound for a non-EU country it could possibly be of a different grade or quality than coal coming into a EU country.
"How will they divide that coal or animal feed? It will cause a lot more problems than they realise."
Truck driver Tom Doherty said it is important to show what a hard border would look like.
Mr Doherty, 57, who travels to Dublin every day from the Inishowen area to deliver fruit, vegetables and potatoes, said truck drivers would face "chaos" and "mayhem" at custom checks.
"I did it up to 1990 and it wasn't nice," he said.
"We don't want to go back to those days of queuing at the border.
"We also don't know what tariffs we will have to pay on potatoes. If I want to avoid crossing the border we have to go by Sligo, and it's an extra three hours driving.
"Who will foot the extra cost? The farmer, customers or me?
"People don't want a border, full stop. The younger generation don't know what it is going to be like."
Mr Doherty, who has been driving trucks for 30 years, is also concerned about the impact on the number of young people who want to work in the industry.
"They're not going to want to sit at the border for hours and I wouldn't expect them to," he added.