Slip sheet. (n.d.). In YourDictionary. Retrieved from https://www.yourdictionary.com/slip-sheet
(plural slip sheets)
(roofing) Sheet material, such as reinforced kraft paper, rosin-sized paper, polyester scrim or polyethylene sheeting, placed between two components of a roof assembly to ensure that no adhesion occurs between them and to prevent possible damage from chemical incompatibility, wearing or abrasion of the membrane.