A wooden fence keeps the horse's safe.
The fence keeps the horses out
If it's to keep the safe it is confining, if it is to keep them out they are not confining but protective.
exists e1 s1 x1 x2 x3.(n_safe(x3) & of(x3,x2) & n_horse(x2) & Theme(e1,x3) & Actor(e1,x1) & v_keep(e1) & n_fence(x1) & a_wooden(s1) & Theme(s1,x1))
exists e1 s1 x1 x2.(n_horse(x2) & n_fence(x1) & a_out(s1) & Manner(e1,s1) & Theme(e1,x2) & Actor(e1,x1) & v_keep(e1))