  We develop an analog of Dugger and Spivak's necklace formula providing an
explicit description of the Segal space generated by an arbitrary simplicial
space. We apply this to obtain a formula for the Segalification of $n$-fold
simplicial spaces, a new proof of the invariance of right fibrations, and a new
construction of the Boardman-Vogt tensor product of $\infty$-operads, for which
we also derive an explicit formula.
