1. I : fset(ℕ)
2. x : 𝔽(I)
3. y : 𝔽(I)
⊢ fl-join(I;x;y) ∈ 𝔽(I)
{ All (RepUR ``I_cube face-presheaf functor-ob``) }
2. x : Point(face_lattice(I))
3. y : Point(face_lattice(I))
⊢ fl-join(I;x;y) ∈ Point(face_lattice(I))