a small or narrow space between things or parts; crevice
See interstice in American Heritage Dictionary 4
(ĭn-tûrˈstĭs)
nounpl.in·ter·stic·es(-stĭ-sēzˌ, -sĭz)
A space, especially a small or narrow one, between things or parts: “There is a gleam of luminous gold, where the sinking western sun has found a first direct interstice in the clouds”(John Fowles).