After the baton is employed, it is closed by hitting the tip of the expandable sections on a hard, solid surface. This pushes the expandable sections back into the handle.
An even more recent development is the AUTOLOCK Baton, again manufactured by Monadnock. Instead of a friction-lock mechanism, it uses a ball-bearing locking system. It can be fully extended by either a flip of the wrist, or by simply pulling the expandable sections out until they click into their locked-open position. A button in the endcap of the baton allows it to be closed very easily by hand, rather than by hitting it end-on on a hard surface. Opening the AUTOLOCK baton by hand offers a tactical advantage in that it is quieter than flipping it open.

information courtesy of http://www.commtechreview.net
Expandable Batons