Overview Reviews Product Description Marking chalk marks are temporary.Provides greater visibility in standard lighting conditions.Durable formula is weather-resistant and suitable for interior or exterior use.Use to show layout changes and corrections on metal, concrete, lumber, plastic, cardboard and other surfaces.Irwin tools strait-line standard marking chalk, 5-pound, blue chalk (65101zr). Irwin Tools Catalog Product Videos Custom Field Manufacturing country CN Product Reviews Write a Review Write a Review × Irwin Strait-Line® Blue Standard Marking Chalk 5lbs 65101ZR Rating * Select Rating 1 star (worst) 2 stars 3 stars (average) 4 stars 5 stars (best) Name Review Subject * Comments *