Always lock your frame and wheel to the bike rack. It's best to have both wheels locked to the rack, but that's not always feasible. We recommend at least the front wheel (preferably both back and front) along with the frame.
Here's a link to great set of resources from the City of Portland with some best practices and links to creative ways to keep your bike secure.
We make our bike rack installations as difficult as possible for thieves to remove or tamper with, without taking extreme measures.
All Huntco flange bike racks are available with a minimum of two breakaway nuts (as shown here, one per side). The Burnside, Sellwood, and Fremont racks all come with four bolts. Security is our priority!