  It has been shown in an earlier work [arXiv:1303.1535] that there exists a
pair of canonically conjugate variables $(f^{ab},N^a_{bc})$ in general
relativity which also act as thermodynamically conjugate variables on any
horizon. In particular their variations $(f^{bc}\delta N^a_{bc}, N^a_{bc}\delta
f^{bc})$, which occur in the surface term of the Einstein-Hilbert action, when
integrated over a null surface, have direct correspondence with $(S\delta
T,T\delta S)$ where $(T,S)$ are the temperature and entropy. We generalize
these results to Lanczos-Lovelock models in this paper. We identify two such
variables in Lanczos-Lovelock models such that (a) our results reduce to that
of general relativity in the appropriate limit and (b) the variation of surface
term in the action, when evaluated on a null surface, has direct thermodynamic
interpretation as in the case of general relativity. The variations again
correspond to $S\delta T$ and $T\delta S$ where $S$ is now the appropriate Wald
entropy for the Lanczos-Lovelock model. The implications are discussed.
