It is proved that, for each
non-negative number β not exceeding the span of a mapping f : X → Y , where X
and Y are compact metric spaces, there exists a non-empty continuum Kβ⊂ X ×X
with identical two projections and such that the distances between f(x) and f(x′)
are all equal to β for (x,x′) ∈ Kβ. Similar results hold for other types of
spans.