Low black leather boots called "boondockers" were issued with the dungaree uniform; however, sailors were allowed to wear black leather jump boots. Flight deck personnel were issued a type of taller cap-toe boot similar in design to jump boots known colloquially as "wing walkers". These types of boots had zig-zag patterned out-soles to avoid gathering "FOD" (Foreign Object Debris) between the ridges that could litter the flight deck and cause potential damage to aircraft. "Dealer/Chelsea" style ankle boots (known colloquially as "Lox boots") with elastic-sides were issued to personnel working with Liquid oxygen for easier removal in case the boots would freeze upon contact.