If you have access to the underside of the flooring, consider
glue/screw a 4X4 to span between the joists below the end of the
knee wall above. Once in place, then drill upward into the end
piece of the knee wall and reinforce it with a long lag bolt
driven upward through the 4X4 into the framing. If you have lived
a good, clean and honest life, you might even find the end framing
member of the knee wall passes OVER a floor joist, making life
even more simple.

Nonny
--
On most days,
it’s just not worth
the effort of chewing
through the restraints..