Last week was a busy one at the Barclays Center in Brooklyn. The rusticated arena lost its shot at hosting the 2016 Democratic National Convention, but there was still plenty to cheer during its first N.B.A. All-Star celebration.

It was a busy week next door, too. Just across Sixth Avenue, past the prefab apartments and satellite trucks, sits a squat gray warehouse that has stood since the 1930s and has been home to Atlantic Wool since 1997.

Inside, Aaron Piller, the second-generation president, was hurriedly sorting, stacking and selling off thousands of rolls of fabric, from $2-a-yard T-shirt cotton to $100-a-yard cashmeres.

“The more I sell, the less I have to move, not that I know where I’m going,” Mr. Piller said on Wednesday.