What is "sackcloths"

Usage examples of "sackcloths".

Then, in sleeveless sackcloths once again, the three infamous operatives regrouped and climbed aboard the mecha that would deliver them back to the SDF-1 and its world of delights.

He regarded the three couched men in sackcloths for a moment, then began to review what they'd told him.

Grouped together on the tabletop and clothed in the only suitable garments available-sleeveless sackcloths cinched at the waist by rough cords-were the three now "micronized" operatives, Rico, Konda, and Bron.