DeckWise Joist tape can be applied to decking joists, around deck support posts, and over ledger boards. DeckWise Joist Tape creates a waterproof seal that helps prevent decay and wood rot. DeckWise Joist Tape is a waterproof wood flashing that uses rubberized asphalt mastic adhesive. When DeckWise Joist tape is applied to the top of decking joists or 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 seals around decking screws to prevent the intrusion of moisture and water.