This talk is on a different subject, and is independent of the talk a couple of weeks ago, but the commonality of "one good leg" calculations will illuminate both. This week we'll do more technical details as we confront approaches to applications that involve more than two systems maintaining synchronisation. This is done via so-called "multilenses". Multilenses were defined by Diskin, and sometimes could be combined (arguablly composed) to form bigger multilenses, but there was no discernable category structure. We'll see how a restriction of multilenses to those with "one good leg" leads to a tractable well-defined composition and a multicategory of multilenses.