Compatable with big brand name racks but will run into issues if you have another kind- in my case a custom rack for land rover. There wasn't enough clearance between my roof and rack to get the clamps to fit. So it took a bit of juryrigging to get it to work. Still, when it did, it worked good. Although, the actual rack itself is considerably less 'solid' then I had anticipated. I would imagine if someone REALLY wanted your gear, chances are they could get it- but not without some work. Hopefully by then, a passer by may hear your car alarm, or you wake up in time enough to ask them if they need any help. Because just as the advert suggests, sleeping in the parking lot is something that some of us do.