WINONA, Minn. –Industrial supplier Fastenal has locked the doors at its 2,200 U.S. retail outlets because of the coronavirus, but online and telephone orders are being fulfilled through the back door, chief executive Dan Florness of the Winona-based company said. The company also has 1,100 onsite locations inside facilities of major customers. Of those, Florness said, 120 have closed because the plants themselves closed. Even so, he said, overall sales so far this year are better than expected due partly to demand for protective health care equipment.