Hi, all: I'm trying to understand the meaning of the term "null-homotopic framing". Say K is a knot embedded in a manifold , and N(K) is a tubular neighborhood of K ( there is a theorem that a compact submanifold allows for the existence of a tubular neighborhood). I read about it here, under " motivation for the Legendrian conjecture " : http://electrichandleslide.wordpress.com/2013/05/17/the-legendrian-surgery-conjecture/ A framing here is a choice ( up to isotopy, I believe; not specified in Rolfsen's book) of isomorphism between the tubular neighborhood N(K) and ## S^1 \times D^2 ##. (Though K can be any manifold for which a tubular neighborhood exists, e.g., maybe the normal bundle N(K) is trivial, or K is compact, embedded in some ambient manifold M) I understand the obvious meaning of null-homologous for a cycle in any space, meaning that the cycle is , e.g., a bounding cycle (cycle with non-trivial boundary) in simplicial homology, so homologically trivial, or different definitions for different choices of homology, but I cannot see what a null-homologous framing is. Any ideas? Thanks.