I would guess they use rear wheel sliding locks [1]. Here in Amsterdam they are really popular. [1] http://austinontwowheels.org/2008/08/06/review-axa-defender

I would guess they use rear wheel sliding locks [1]. Here in Amsterdam they are really popular. [1] http://austinontwowheels.org/2008/08/06/review-axa-defender-rear-wheel-lock/ http://austinontwowheels.org/2008/08/06/review-axa-defender-...