Here's a short StreetFilms piece on bike corrals (and bike oases). It includes some interesting shots of how they implemented this in PDX. A physical barrier (like bollards) ringed the parking spaces and they put down a temporary rack to lock to. I wonder if Dero or anyone makes such a rack locally, and I wonder if these can be rented. Cost of implementation will be a challenge we need manage if a bike corral at 48th and Chicago is going to get off the ground.