A quilt on a fence in front of a cabin might be used, for example, to tell escaping slaves that the cabin was safe to approach. No quilt on a fence might indicate the need to stay hidden until the quilt (safety) appeared. The next part of the story is more controversial.
It is said that certain quilt designs (such as Jacob’s ladder, bear’s paw, flying geese, star/north star/evening star, log cabin and others) gave the escaping slaves explicit directions, such as 'gather the tools you want', 'we leave tonight/tomorrow' or even 'go three miles north, up the bear’s trail and then head west'. According to one theory, the knots on a quilt and the place where they were located would give specific information on how many miles to go and in what direction.
In 1993, the African-American quilter Mrs. Ozella McDaniel Williams, of Charleston, South Carolina, told historian Jacqueline Tobin that she knew of ten quilt designs, passed down through her family, that were used in this way. But some scholars are skeptical about this and about comparable 'inherited' memory/information.
Source: TOBIN, Jacqueline L. and Raymond G. DOBARD (2000). Hidden in Plain View: A Secret Story of Quilts and the Underground Railroad, New York: Anchor Books/Random House.
Digital source of illustration (retrieved 30 June 2016).
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