TORONTO (AP) — The truck blockade at the U.S. border by Canadians protesting the country’s COVID-19 restrictions is tightening the screws on the auto industry, forcing Ford, Toyota and General Motors to shut down plants or otherwise curtail production. The bumper-to-bumper demonstration entered its fourth day Thursday at the Ambassador Bridge connecting Windsor, Ontario, to Detroit. It is disrupting the flow of auto parts and other products back and forth across the border.