WiseWrap JoistTape by DeckWise is a malleable polyethylene waterproof wood flashing and material, using a rubberized asphalt mastic adhesive. Each roll measures 3" wide by 75' feet long and specs out at 35-40 mil thick. Easily apply to decking joists, around deck support posts and over ledger boards. When this tape is applied to the top of decking joists, over ledger boards, and around support posts, it creates a waterproof seal that helps stop decay and wood rot. Rot is caused by moisture that stays in contact with treated and untreated lumber deck framing and the above decking material. Wood decay can also occur when deck screws penetrate the deck boards, piercing the joist sub-framing below. The application of WiseWrap JoistTape will also seal around decking screws preventing the intrusion of moisture and water