[en] From the particle physics point of view string theory may be considered as a theoretical framework to describe further resolution of vertices by means of intermediate surfaces, like gauge theories may be considered as theories of intermediate vector bosons resolving 4-Fermion vertices. In this contribution the topic of Fock space representations are a necessary ingredient for the development of applications of string field theory, and an improved understanding of Fock space representations shed new light on more fundamental issues of string field theory. The conditions of mutual alignment and annihilation of string sectors are expressed ed in terms of overlap conditions in the Fock string modes with closed strings. The results prove the versatility in solving the overlap conditions for the Witten vertex and in Fock space calculations of its properties