This IRWIN STRAIT-LINE Permanent Marking Chalk is designed for exterior use. The marks are visible after weeks of weather exposure and jobsite wear.
The 65102 Strait-Line 5lb Red Chalk is what you need to help get things Strait. The Strait-Line 2.5lb blue chalk is great for outdoor use, carpentry, bricklaying, masonary, roofing,carpet installation,floor and wall tiling, painting, decorating and many other uses. Red chalk is what you would need for a permanent line that will be able to endure the elements of the environment. For more than 30 years, Strait-Line products have represented the standard for excellence and performance in marking tools.