Velcro tape lol. I only put it on when I park, really just in Denver. The parking people are assholes about the front plate. I got a ticket right after I bought the car for no front plate, then the next time I tossed it in my window and got an "improper front plate" ticket. It's been working just fine so far, I'm not about to drill holes in my bumper for the stock mount.
I'll buy the perrin if it becomes a problem but I have yet to get pulled over while driving
You can see the little square on my front bumper