Many rollers still rotate when blocked, so as not to roll, these two block. But as others have mentioned, you'll probably have to bend down to unlock them because when the lever is FULLY locked, it's vertical and close to the wheel. You might not have to push it that far! PS: the screws and washers are a joke, although the screwdriver is pretty good quality for a freebie. The holes in the mounting plate are large enough for the washer to fit in the hole (when tightened securely). The mounting holes are oversized for the nominal weight or the included screws and are suitable for lag screws 1/4"=6mm.