Knit fabrics are used for a variety of technical and industrial applications. Ground covers made of warp knit fabrics protect golf courese from the adverse effects of winter weather. In Europe, warp knit fabrics filled with sand act as sound barriers around tennis courts. Warp knit fabric coated with resin serve as covers, tarpaulins, accordion roof units, and soft sides for trucks. Warp knits are being used increasingly in protective clothing for firefighters, SWAT teams, and bomb disposal squads. Filtration is probably the largest single application for circular knit fabric in the nonapparel field.