Aeration Marking Flags Blackburn Mfg. makes marking flags and rigid markers and sells them at factory-direct low prices! Order marking flags now for spring aeration. Blackburn makes plain and printed flags in 15 colors. Have your company's name and logo printed on your flags and turn them into an inexpensive marketing tool. Turnaround, even for custom printed flags, is completed within 10 days of order. Get factory-direct lower prices on marking flags at www.blackburnflag.com or call 800-942-5816.