C22b=bo is the largest constant for which one has an inequality
L≥boC
for all knots that admit an alternating diagram, where L is the ropelength of a knot (or link) with crossing number C.
The ropelength L is the infimum over all embeddings of the knot (or link) of the ratio of the contour length of the knot to its thickness. The thickness is defined as the radius of the smallest circle that passes through any three points on the knot (where collinear points yield an infinite radius). Colloquially, the ropelength is the least amount of rope required to tie a specific knot in a rope of unit radius. See [CKS2002] for the full definition.