Better than straps or rubberbands around hand brakes as a parking brake , take a strip of velcro, and a strip of the fuzzy recieving stuff, and sew them back to back into a single strap. Then put the strap around the front wheel and the down tube. The bike will not roll when leaning against a vertical surface and, if that vertial surface is a thin tree or post, the front wheel wont turn and allow the bike to fall when you aren't looking.