Module KL := KL'.
Instance Join_nat_F: Join (nat * F predicate) :=
Join_prod nat  (Join_equiv nat) (F predicate) _.
Instance Perm_nat_F : Perm_alg (nat * F predicate) :=
@Perm_prod nat _ _ _ (Perm_equiv _) (Perm_F _).
Instance Sep_nat_F: Sep_alg (nat * F predicate) :=
@Sep_prod nat _ _ _ (Sep_equiv _) (Sep_F predicate).
Instance Join_knot : Join knot :=
Join_preimage knot (nat * F predicate) Join_nat_F unsquash.

Lemma join_unsquash : forall x1 x2 x3,
join x1 x2 x3 =
join (unsquash x1) (unsquash x2) (unsquash x3).