ELK Anti Slip Tape Heavy Duty 80 Grit High Traction Nonslip Griptape Adhesive Non Skid Treads for Steps, Staircases, Hardwood Flooring - Indoor and Outdoor Use (4 Inch x 33 Feet, Black) - Amazon.com
Pure Garden Patio and Deck Tiles– Interlocking Stone Look Outdoor Flooring Pavers Weather Resistant and Anti-Slip Square DIY Mat (Grey Set of 6) - Walmart.com