EXLEAF Trim Guard 12 Inch Paint Shield,Edge Painting Tool for Walls,Paint Edger Tool for Precise Trimming (Blue)

paint shield/trim guard. you can get them pretty cheap at any big box store, amazon, hardware store, walmart, etc. like this: https://www.walmart.com/ip/EXLEAF-Trim-Guard-12-Inch-Paint-Shield-Edge-Painting-Tool-for-Walls-Paint-Edger-Tool-for-Precise-Trimming-Blue/20251514666 you can also use cardboard in a pinch, in fact they have cheap cardboard ones at some stores. i prefer to use the thinner paperboard like they use for cereal boxes. if you get a box with a slightly shiny outside, you can wipe it off easier between uses with a slightly damp rag to keep your edge clean.