  We solve the dual multijoint problem and prove the existence of so-called
"factorisations" for arbitrary fields and multijoints of $k_j$-planes. More
generally, we deduce a discrete analogue of a theorem due in essence to
Bourgain and Guth. Our result is a universal statement which describes a
property of the discrete wedge product without any explicit reference to
multijoints and is stated as follows: Suppose that $k_1 + \ldots + k_d = n$.
There is a constant $C=C(n)$ so that for any field $\mathbb{F}$ and for any
finitely supported function $S : \mathbb{F}^n \rightarrow \mathbb{R}_{\geq 0}$,
there are factorising functions $s_{k_j} : \mathbb{F}^n\times \mathrm{Gr}(k_j,
\mathbb{F}^n)\rightarrow \mathbb{R}_{\geq 0}$ such that $$(V_1
\wedge\cdots\wedge V_d)S(p)^d \leq C\prod_{j=1}^d s_{k_j}(p, V_j),$$ for every
$p\in \mathbb{F}^n$ and every tuple of planes $V_j\in \mathrm{Gr}(k_j,
\mathbb{F}^n)$, and $$\sum_{p\in \pi_j} s(p, e(\pi_j)) =||S||_d$$ for every
$k_j$-plane $\pi_j\subset \mathbb{F}^n$, where $e(\pi_j)\in
\mathrm{Gr}(k_j,\mathbb{F}^n)$ denotes the translate of $\pi_j$ that contains
the origin and $\wedge$ denotes the discrete wedge product.
