I've had a couple different chalk lines and this one was by far the most frustrating I've used. The line got stuck so many times I knew how to take it appart real quick. The all plastic mechanisms inside wore down real quick and it didn't hold up very well at all. After doing a single roof with it I threw it out, purchased new string for my old one and still have it.Whether it'll handle a drop from a roof ... I don't know ... was tempted many times to throw it off the roof.Highly recommend not buying this product. There are plenty of good chalk lines on the market. This is living proof that looks aren't everything.Hope this email didn't sound too negative.I hope someone reads this and saves their money.